Notes: I originally posted this fic under an old account on December 13, 2010. This is a revised version.

Modus Operandi

-x-

It leaves nothing behind, and nothing is perfect.

-x-

Both of them were famous in their own right. He was the Boss's son and the automatic successor of the Organization. She was Hell Angel's daughter and a leader in biomedical research. He designed most of the high-level operations for the Organization, and she advanced techniques to lengthen or shorten people's lives. Neither had expected their paths to cross, but when they finally met, both disliked each other instantly. To him, she was standoffish and a threat to his job. To her, he was conceited and dismissal of her work.

"You lot should stay in your labs," he was saying, "where you belong."

In contrast to his sharp voice, hers was fluid and quiet but simmering. "This drug was developed specifically to aid your – "

"This drug," he hissed as he rattled the bottle of pills, "is undetectable in the human body."

The strawberry blond narrowed her eyes to hide her surprise and confusion. From their earlier exchange, she'd assumed he'd come to the meeting completely oblivious of the report documenting her work. She reflected on his words and the task she'd been given. "Isn't that your goal?" she asked slowly. "To commit the perfect crime? Apoptoxin cannot be traced – " she cut off abruptly when he gestured angrily.

"That's the problem," he snapped and smacked the pill bottle against the top of the desk between them. "Apoptoxin is too perfect. One healthy person dropping dead for no apparent reason is okay, but a hundred of them happening at the same time is going to raise suspicion. Besides," he continued as he snatched up her report from the desk and fumbled for the table of numbers, "the success rate for lab rats is only 98%. That's low. That's crap. And this – " he flipped two more pages and shoved the document into the chemist's stoic face " – I want to know what happened to the 0.7% of the rats that didn't die. What the hell does 'abnormal regression' mean, and how does it translate over to human beings?"

Her expression remained impassive as she forced her clenched fists to remain on her laps, but her gaze was hard and cold. His concern was valid, and the results had troubled her as well. 140 rats had survived out of a sample of 7000; one rat had not only survived but also returned to its infancy with no other apparent side effects – yet. Poor statistics prevented her from drawing a solid conclusion: whether the drug had deeper problems or whether the case was just a fluke. She took a deep breath and countered his statements one by one.

"Apoptoxin is a tool at your disposal, and like all tools, using it requires some intelligence." She raised her voice when he opened his mouth to protest. "Nobody ever told you to use it a hundred times in a row. Use it on that one person in your life that you can't kill otherwise, or even chuck it; I don't care." In truth, however, she did. This project had derailed her from her original research, cost a lot of time and money, and failed to produce the results that she, or anybody, had wanted. "All the rats that survived are undergoing genetic testing so that we can find out what is wrong with apoptoxin, if it is anything that we can change at all. As for 'abnormal regression,' we still do not understand the effects or we would've explained it. I sincerely apologize for science's ignorance and my staff's incompetence," she said sourly and added, perhaps a second too late, "Sir."

He opened and closed his mouth several times as he struggled to find something to say. No one had questioned his authority or decisions before, and she was the first to insult him in his face. It was refreshing, but mostly infuriating. He frowned when she mockingly raised an eyebrow at his speechlessness. "Sherry, was it?" he finally said and smiled, which would've been charming on any other occasion if fury wasn't boiling in his eyes. The command was staccato. "Go back. To your lab."

She returned the smile with a sweet and polite one of her own, but she might as well have given him the finger. "Have a nice day," she said lightly, rose to her feet, and turned her back on him.

They exchanged another glance before she clicked the door shut behind her, and both muttered to themselves, "Cute face, but what an asshole."

-x-

For the most part, he worked solo and from his office at the headquarters. Sometimes, he would consult specialists – toxicologists, computer scientists, electrical engineers – but they were sources of information, not "partners." Even when he did field work, his partners, more frequently known as "backup," changed depending on the operation. It didn't mean he lacked favorites, however, and currently, the top choice for his next mission was immobile and on life support.

"Caught in her own explosion that detonated too soon," were the doctor's words when he heard the news.

Machines beeped and hummed in the room as he stood against the wall and tucked his hands into his pockets. His gaze trailed to Merlot's face wrapped heavily in bandages; only her brunette hair, much of it lost to flames, was visible. The doctor thought it was amazing that she'd survived, but he found it more amazing that they'd bothered saving her. Merlot was the Organization's bomb expert and knew more about circuits than anyone else he had met, but despite her invaluable skills, she was also slightly psychologically unstable. She had yet to jeopardize her operations, but the higher-ups of the Organization had debated for a long time whether to dispose of her directly or to let her kill herself in one of the explosions she designed. One side was afraid she would one day leave a crack that'd put the Organization at stake – the rumors that a detective was investigating the Organization didn't help – whereas the other deemed her skills indispensable ("until an inevitable, tragic accident").

He sighed and pushed himself away from the wall. Regardless of what the Organization was planning, he needed to find a replacement for Merlot and soon. "Maybe Vermouth," he muttered as he reached for the door and paused with a frown when footsteps and low murmuring approached from the other side. He stepped back as the door swung open, and he scowled when he recognized the strawberry blond. Behind her was a nurse. "You again," he said. "What are you doing here?"

The chemist had started when she nearly walked into him upon entering the room, but her composure returned as soon as she realized who he was. Her right hand slid away from the door handle and picked up a small pill box resting on the clipboard held in her left hand. Glancing at patient on the bed, she said, "Merlot is the first human test subject for apoptoxin."

"Before it's even completed?" he asked and stared at the pill box with a raised eyebrow.

She seemed offended by his incredulous tone and didn't attempt to hide her annoyance. "Our last conversation was two months ago," she said. "In the meantime, we've managed to isolate a few genes common to the rats that survived but lacking in those that died, so even though we haven't completed the prototype to address this issue, we have a hypothesis as to when the current version would work. We've been ordered to move on to human testing."

"And Merlot would work?"

She hesitated and looked away. "We don't know yet," she said in a quiet voice and looked up again before he could complain. "We received a sample of her tissue yesterday after the surgery, and we're waiting on the lab results. It'll be interesting whether it works or not." She glared at him. "Now will you move out of the way?"

He furrowed his brows but didn't budge, which earned him another glower, but he spoke before she could. "Can I stay and watch?" he asked, almost innocently, but genuinely curious.

The chemist gave him a strange look, considered his request for a moment, and nodded her head. "Just don't interfere," she added as a warning.

He rolled his eyes as he pulled up a chair and mumbled something about touchy scientists. She glared at him again and extended her hand to the nurse behind her for a small beaker, a stirring rod, and a syringe with a needle. He stretched his legs, settling into a comfortable position, and watched as she stirred the pill in clear liquid until the former disintegrated.

"Would injection affect the symptoms?" he asked as the chemist filled the syringe with the murky solution and passed it to the nurse.

"Only the speed at which the drug takes effect," she said, not taking her eyes off the syringe while the nurse found Merlot's vein and pierced the needle through the skin. The strawberry blond turned her head to the cardiac monitor, causing him to do the same, and watched as the steady pulses slowed to a still, all before the nurse could remove the empty syringe.

He blinked and then leaped out of his seat, pushing the chemist away from the bedside, to peer into Merlot's face, which was regrettably covered in bandages that hid any immediate contortions from pain. Not that she would've been able to show any in her unconscious state, he realized belatedly. As far as he could tell, Merlot didn't respond to apoptoxin in any manner, not even a twitch, but he didn't know if it was because she was registering pain while unconscious or because there was no pain to register. "Shit," he said. "That was practically instantaneous." He turned to the strawberry blond. "No pain?"

"None as far as I know," she replied with a distant expression. The rat that'd regressed had certainly displayed signs of immense pain, but she gathered it was probably due to the physical transformation and not the drug. "And yes," she continued, "it's fast, even when it's ingested."

"What's the time delay?"

"A few seconds."

He stared at the strawberry blond for a moment and shifted his gaze to Merlot, who looked the same as before if not for the cardiac monitor announcing her death with a monotone pitch. He flipped off the switch and said, without looking at her, "Next time you test apoptoxin on a conscious human being, tell me. I want to be there."

She snorted. "Now you're interested?"

He narrowed his eyes and met the strawberry blond's gaze. "I'm interested in identifying deaths by apoptoxin – through other means if not autopsy."

"You can't," she stated. "If it's successful, it's perfect. There is nothing."

He closed the distance between them, ignoring the discomfort on her face, and lowered his voice. "That 'if' is your number one problem. There'll be more." Without waiting for a response, he stepped past her and exited the hospital room.

-x-

Her office door was open when he arrived the next Saturday afternoon, and he found her sitting at her desk facing the door with her brows furrowed. He stood in the doorway with one arm propped against the door frame and waited for the strawberry blond to notice him. A few seconds later, when it became apparent that she was too engrossed in her work, he sighed and cleared his throat. She looked up in response and shot him a dirty look.

"What do you want?" she asked, cranky.

"I want you as my backup for tonight's operation."

"No," she said. "Go away." When he gave no indication that he'd leave anytime soon, she added, "What happened to 'You lot should stay in your labs, where you belong'? I'm busy with my own work." She glanced down at the report in front of her and tried to focus, but his annoying presence was almost impossible to ignore. Sensing an impending headache, she closed her eyes and tried to remember the pressing issue at hand. The report mentioned something about genes. The genes of the rat that regressed –

"Merlot was supposed to be tonight's backup," his voice sliced through her thoughts and she twitched, her eyes snapping open. "Seeing as you're the one who ended her life," he continued casually, "I figured you can be her replacement. It's also a good chance for you to see how I work."

She heaved a sigh and rubbed the bridge of her nose, exasperated by his logic. "You didn't protest her death," she said.

He shrugged. "It wouldn't have made a difference, whether she was unconscious or dead. I would need a replacement either way."

"Who would be the replacement if she hadn't died?"

"It doesn't matter. She died because of your work, so you're coming with me."

"And if I refuse?"

There was a long pause as they stared at each other, one confrontational and the other weary. Frustrated, he looked away for a brief moment, scratching the back of his head, and turned to the strawberry blond again. "Look," he said. "Don't push me. Are you coming or not?"

She opened her mouth to say "no," but something in his gaze stopped her, and she narrowed her eyes in distrust, suddenly afraid for her sister. "Is that a choice?" she asked.

"Not really, no. But you're better off thinking that it was, so pick the right one."

The strawberry blond leaned back in her seat and crossed her arms in front of her chest. "What's the operation?"

"Simple. Be my girlfriend for the evening."

The chemist nearly choked on air. "What?"

Sighing loudly, he tossed a pointed glance down the hallway and said, "Can I come in and close the door?"

She stiffened, feeling her heart pound against her chest, but she forced herself to relax – or at least appear so – and replied without looking at him, "Yeah, sure."

The door closed with a quiet click, and he pulled out the chair across from her. "The target is an old neighbor of mine," he explained. "Pose as my girlfriend when we visit him for dinner, and then keep the old man occupied for at least half an hour, preferably in his basement lab. I'll take care of the rest."

The strawberry blond eyed him warily. "Keep him occupied, how?"

His smile was devious. "However you want," he drawled and broke into laughter when he caught sight of her disgust. "Don't take it the wrong way," he said, amused. "The old man is an inventor, so talk science and engineering with him. Approve of his work. Give him more ideas, like tracking glasses. I don't know." He tilted his head to the side and muttered, "Tracking glasses would be nice to have, actually. If they work." They exchanged a glance, and he continued, "Anyway, you see why I preferred Merlot. She built hardware, so she was well-versed in his language. Plus," he added with a wry smile, "she was more attractive than you are."

"Before she tried to blow herself up," she remarked dryly and he grinned at her statement. She raised an eyebrow and decided to push her luck when curiosity got the better of her. Even if it did go too far, she'd have a handy excuse. "Were the rumors true – that you were dating her?"

"Oh god, no. She was nine years my senior, and have you ever talked to Merlot?" He crossed his eyes. "She was always incoherent unless she was building circuits or playing with explosives. Probably would've suggested diet coke and mentos for this operation if she was feeling sane and liquid nitrogen bombs if she wasn't. But then again, if I were going with Merlot, she would've been the one doing the work while I distracted the old man." His expression sobered, and he shifted in his seat. "Carbon monoxide poisoning because of his kerosene heater, that's how he's going to die."

The strawberry blond's expression was unreadable, and her voice was quiet when she spoke. "You said he's your old neighbor. Do you know him well?" Several minutes ago, she wouldn't have asked this question, but after their chat about Merlot, something in the atmosphere had changed. He wasn't just an obnoxious "Sir" or "the Boss's son" anymore. She thought of her sister and, for the first time, wondered how the teenage boy in front of her had grown up.

He pushed himself to standing and gave her a dark look. "This isn't time to get sentimental. We're only following orders. There's always a reason why the Organization wants someone dead, and if I'd felt sympathetic, I would've chosen a painless death for him." He turned and opened the door, where he paused and looked at her over his shoulder. "Meet me at my office at 5:30pm. Dress casual."

"Carbon monoxide poisoning doesn't guarantee death," she shouted after him and jumped up from her seat, her palms pressing firmly against the top of her desk. Her office chair rolled backward until it hit the wall with a clack. Suddenly, she felt very silly and wondered why she cared to know if the Boss's son was a normal human being when it came to emotions. Even if he did, she reasoned, a neighbor could just be "the person next door" in the same manner that yesterday's target was "the person on 7th street."

His face was shockingly calm when he halted his footsteps and turned half-way around at the doorway. "Is that a problem? Accidents are hardly 100 percent. It'll be my first time staging a murder as an accident, and if it fails, I'll learn from the flaws. I doubt it will, though. I've gone over the scenario more times as a detective than as a criminal, so you can relax." He raised a hand. "See you later."

-x-

She had been taken aback by Agasa Hiroshi's jovial personality, but she'd managed to shut out her emotions before her stomach could churn, before she could feel sick sitting at the dinner table, watching what could've been daily life. Their target was going to die in an accident – the fatal combination of a malfunctioning kerosene heater and a carbon monoxide detector with a dead battery – and they had nothing to do with it.

She had nothing to do with it.

"Do you want to get coffee?" he asked after they bid goodnight to the old inventor and started walking down the street. When the strawberry blond gave him a puzzled look, he added with a smile, "Might as well make it a real date, right? Cafe Poirot is nearby." He nodded to the left and held out his arm.

She glanced at his arm and then gave him a long look. "Do you always do this after an operation?" she asked quietly. What do you feel?

He blinked, and his eyes glistened as his smile became enigmatic. "What operation?"

There was a pause before she let out a soft laugh, partly defeated and partly sad, and took his arm. She should've expected as much; they were in the same boat of moral ambiguity after all. "Your treat," she said, and he grinned. For the first time, she noticed how much taller he was than she. "Is 'Shinichi' your real name?" she asked as they walked. It was what the inventor had called him, and even though she was introduced with a fake name that they'd agreed upon prior to leaving the Organization headquarters, she wondered about his.

He made a sound that meant nothing in particular. "Is it?" he asked.

"You know my real name."

"It's in the files."

She watched him from the side, but he kept his gaze forward as he led them across the intersection and turned left. The street lights did little to illuminate his thoughts, and she decided to drop the subject. It helped to connect his face with a name that wasn't "the Boss' son" or "Sir," but whether or not it was his real name probably didn't matter. He'd never called her by her real name either, and likely never would.

They walked down the last two blocks in companionable silence and arrived at the cafe. She hesitated briefly when she caught sight of the sign "Mouri Detective Agency" above the cafe, but he didn't seem bothered. He was calm. He was always calm and confident.

He held the door open and gestured to her to enter first. The cafe was larger and busier than she'd expected, and she realized it also served as a restaurant. He directed her to a table for two by the corner window and picked up the menu as he slid into the seat facing the room.

"Do you come here often?" she asked as she studied the menu in her hands.

"Sometimes," he murmured absentmindedly. He closed the menu and looked at the strawberry blond. "How's your research going?"

She looked up with a raised eyebrow. "I thought we were on a date."

He folded his arms on the table and leaned forward. "You were really preoccupied with your work earlier. I'm just wondering why."

The chemist felt a flash of annoyance as she remembered the troubling report and forced her gaze down at the menu again. "What's good here?" she asked, indicating the menu.

"Their latte," he said and looked past the strawberry blond's shoulder, slightly distracted. He leaned back in his seat with a polite smile, and she glanced up at the waitress headed in their direction. After they gave their orders and the waitress was out of earshot, he continued, "I thought of a possible application for your research, so I'm curious about the timescale."

She furrowed her brows and clasped her hands together as she weighed her words. "I thought you weren't interested." Her head jerked in response to a man pulling out the chair at the table next to them, and she saw his gaze linger on the man as well.

"What timescale are we talking about?" he asked, his attention returning to the strawberry blond.

"It depends." She paused when the waitress set two cups of latte in front of them and took orders from the person at the next table. "You know how it works," she continued when they had reasonable privacy again, vaguely irked that he wanted to discuss this matter in public. She didn't trust that they would comprehend each other's cryptic message, but she also began to suspect that the Boss' son might not be socially competent enough to talk about anything but work. Not that they had much in common otherwise. "And you know what we need to check," she added.

"When will it reach the stage where we wouldn't have to check?" He stirred his latte and set the spoon to the side after tapping it against the edge of the cup three times to shake off the liquid and cream. He took a sip and waited for an answer.

She refused to meet his eyes as she picked up her cup and stared at the floral pattern on the surface of the cream. The report, mostly theoretical, had demonstrated that it was impossible to predict when apoptoxin would kill a rat or merely cause it "to shrink." Lab results also suggested that the rat that regressed should've died given its genome. In other words, they understood when apoptoxin would be effective, but they had absolutely no control over what that effect would be. 0.015% of the cases would survive apoptoxin without their knowing, but how regression in rats would translate over to human beings still remained an unknown. If the statistics were correct, they would need an impractically large sample of human test subjects. She nearly jumped when the man next to them sneezed.

"Bless you, sir," he said, amused. The man nodded in appreciation as he wiped his nose with a napkin.

She returned her drink untouched to the table and debated how to explain the problem with apoptoxin to him. A motion in her peripheral vision grabbed her attention, and she found herself staring at a trickle of liquid rolling down the window. The viscosity of it was higher than water, and her eyes trailed upward where she discovered more of it dripping down. A car drove by, briefly lighting up the surrounding area, and the chemist could see that the liquid appeared dark instead of transparent. It almost reminded her of blood.

Before she could open her mouth to say something, the whole world seemed to take notice of the peculiarity at the same time. A woman outside screamed and pointed above the cafe window, catching other people's attention. A crowd began to gather on the sidewalk, creating a commotion, and the people in the cafe started to whisper among themselves. A man burst into the cafe and shouted, "There's a dead body hanging out the second-floor window!"

There was a loud gasp, and the cafe was in an uproar while some people rushed outside to look. He grabbed her arm from across the table, his strong grip telling her to stay put. The strawberry blond gave him a confused look, but his gaze was fixed on the crowd outside the window.

She leaned forward and asked him in a low voice, "What are we going to do?"

"Nothing," he replied, still watching the scene outside. "The cops will come, and they'll question the people here – us included. If we leave now, we'll look suspicious. Just like the person who was sitting next to us."

She twisted her head to the left and found an empty table. Her eyes swept the room and then the crowd outside.

"He's gone," he said.

Police siren came wailing from a distance, and soon, the neighborhood was flashing blue and red as law enforcement sealed off the sidewalk and directed the crowd into the cafe.

"Why didn't you stop him?" she whispered.

"Why should I?" he countered, his expression serious but his eyes feverishly bright, almost psychotic.

Realization dawned on the strawberry blond as she put together his earlier behavior, and she stared at him in horror. "Did you set this up? The second floor – "

He tightened his grasp on her arm and narrowed his eyes in warning.

The second floor was a detective agency. There was a detective investigating the Organization. A weak point in the Organization. Agasa Hiroshi. Accident. Cafe Poirot. Mouri Detective Agency. Murder.

"Let go," she said through her clenched teeth.

-x-

They didn't see each other again for a month after the incident. Her lab had sent him two memos in between, one to inform him of the second apoptoxin test and another three days later to tell him that the test subject Numabuchi Kiichiro had escaped and therefore the test was canceled. He'd made an irritated face at the memo and fired off a stern email to the security, but the matter slipped his mind for the next two weeks until a third memo hit his desk one morning.

It was from the higher-ups, announcing the suspense of all research under Sherry's lab because of "funding and discipline issues." She'd challenged the Organization. Aggravated but not surprised, he threw the memo onto his desk and stormed out of his office, making his way to the basement prison chambers.

Her gaze was filled with hatred when he flung open the door to her chamber.

"What did you do?" he demanded.

"Why did Gin kill my sister?"

He narrowed his eyes. He remembered the report from a few days ago documenting the execution of Miyano Akemi for defying the Organization, but he hadn't spared it a second glance. "What did you do?" he asked again, the temperature in his voice dropping a degree.

"Tell me why he killed my sister."

"What – " his voice fell to an icy whisper " – did you do?"

She yanked on the chains binding her wrists to the wall, wishing that looks could kill but knowing that even if they could, hers was not enough because there was too much grief washing out the rage. "Why did she have to die?" she shouted, hating the tremor in her voice, the tears rolling down her cheeks, and the fact that the man before her could easily get his answers elsewhere whereas she couldn't.

"Why do you care?" he suddenly asked in bewilderment.

She inhaled a shuddering breath, as if she'd just been slapped by the raw incomprehension in his tone. Wide-eyed, she stared at him, feeling a chill spread through her body.

"Because she was your sister?" he continued. "But why should that make her special? If Numabuchi had tried to buy his way out of the Organization and was shot because of it, would you be doing the same thing? It's not very fair, what you're doing." He paused, taking in her colorless face and trembling body. "Never mind, I'm no longer interested in what you did. Apoptoxin – we need a new test subject. Why don't you offer yourself to try out the drug you developed? The drug that, you claimed, is perfect because it leaves nothing behind?"