Interrogation was a formality, but one that Kate planned to see through to the end, even if the DA's office could file charges based on forensic evidence alone and get a conviction.

Sometimes it wasn't about taking the easy road, and given that she still hadn't shaken the mental image of a killer with a knife to her husband's throat, she was beyond ready to rattle a cage.

Standing by the door to interrogation, Kate sucked in a deep breath, centering the storm of emotion that had churned inside since she had seen Castle run onto the path and be followed immediately by the clown that had materialized from the treeline to walk in her husband's footsteps. While maybe not as dangerous as the other challenges they had faced together, the image was one that she couldn't easily shake.

There had always been so much to lose where Richard Castle was concerned but now it was unfathomable.

It was about more than just him, or her, or even the two of them as a unit. Now it was another life, another person who would grow up needing a mom and a dad to teach him or her about the world and everything in it.

Blowing out a long sigh, Kate forced herself to stop dwelling on the could-have-beens and simply appreciate that the killer had been apprehended. If nothing else, they had saved one more family from grief. Cameron Warrington had turned up safe at home, curled on the couch with a two-year-old and an infomercial muted on the television. So if she and Castle both had a certain haunted quality to their eyes when the sun rose and a new day began, at least it was with some measure of success.

"Tell you what, Kate," Castle spoke as he walked over from the bullpen, licking the stray crumbs of the donut he had foraged for breakfast off his fingers. "You play good cop, I'll play bad cop," he grinned, overplaying for the moment in an attempt to chase away the shadows that swirled around them.

The snort she gave was certainly half-hearted, the memory too heavy to jump to glib cop humor just yet, but she lifted her head anyway and fixed her husband with a stern glare. "You can't play cop if you aren't one, Castle," she said, something in her heart easing at the way his lips twitched with the smudge of a smile, just a hint of sparkle coming back to his eyes.

They would get past this one, just as they had so many times before.

And with that on her mind, Kate opened the door to interrogation.

A night in jail hadn't done Tessa any favors. The orange jumpsuit made the shadows under her eyes stand out, the vibrancy of the prison uniform giving her skin a pasty yellow tinge that clashed with the dark brown hair skimming her shoulders. She had been patched up since Kate had last seen her, the bulge of a bandage visible under the jumpsuit and her right arm wrapped in a sling that had to make wearing handcuffs an uncomfortable experience given the angle they were cutting into her skin.

"We'll make this quick," Kate said, dropping the file that had been compiled on Tessa's two murders and the assault on Castle onto the table. "Uniforms searched your apartment last night and found the false bottom in your dresser. We can match the clothes and the wigs in that drawer with the clothes the assailant was wearing at the murders of Olivia Fabre and Levi Graves. The knife you used to cut Mr. Castle last night in Prospect Park has tested positive for DNA from those two victims, and it's only a matter of time until additional testing confirms that the stab wounds are a match to the murder weapon."

"Mr. Castle?" Tessa gave a snort at that, the chains binding her to the table rattling as she pulled at her handcuffs. "I know you're married. Everyone does."

Spreading her hands out in front of her, Kate shrugged her shoulders in Tessa's direction. "We have enough evidence for a conviction…."

"So go on then," the woman challenged. "If you've got it all figured out, just get on with it. I don't want to talk to you."

"Oh, that's not true," Rick said, meeting the eyes of the woman who had loomed over him hours before and been happy to slit his throat. "I think you want to talk, but not about Olivia and Levi."

Picking up Castle's cue, Kate opened up the folder, tugging out a yearbook photo of Anthony Deveney as a fresh-faced junior. With shaggy brown hair, a light dusting of freckles, and vividly green eyes hidden behind a thick pair of glasses, he was a teenager who gave off a vibe of intelligence. Just as Chief Kemper had described, Anthony seemed a kid who was both smart and very nice, if slightly unpopular.

"That's okay," she said with a glance at Castle, holding up the photo for Tessa to see. As she expected, the woman reacted at the sight of her dead cousin, her eyes going glassy with tears even when her mouth stretched into a harsh line and her jaw flexed in anger. "Let's talk about Anthony Deveney. I believe you know him."

"Knew him," Tessa corrected, her voice carrying a distinct note of agony and grief. "Anthony died two months ago."

"And he was your cousin," Rick said, mustering up his best show of sympathy. "Someone you grew up with and loved very much after his parents took you in when your parents died."

Her eyes darted between Beckett and Castle in turn, attempting to judge how much of her life and background that they might know, and for the first time there was a certain level of panic in the chocolate brown irises.

"So what if I did…." Tessa muttered.

"Well, you see, we've found that in the case of murder, it's usually for a few reasons: love, greed, anger, lust. And you fall into the first. You loved Anthony, and you wanted to make the people that you thought hurt him pay for what they did."

It was fascinating to watch Tessa's face change from a classically pretty woman swamped with grief to a furious, bitter girl who choked back her tears to bare her teeth at them. "That I thought hurt them?" she snapped Kate's quote right back at her, smacking a hand onto the tabletop. "Anthony was my best friend, and they ruined his life. A stupid prank because a girl had a crush on him and they couldn't stand it. He spent the rest of his life being spoon-fed and wearing adult diapers because a pair of teenage jocks thought it would be funny to dress up in costumes and chase him through the woods because he liked a girl who just happened to return the sentiment."

"So they deserved what they got, huh?" Kate asked, dropping a photo of Levi's body onto the table and then adding Olivia's. "A knife to the back; a slow, painful death because you decided that they had to pay for their crimes?"

"My Aunt Maggie and Uncle James both worked two jobs just to pay for Anthony's medical expenses and home health care after the bank foreclosed on their house, and my uncle lost his job with the city for missing too many days because they had no one to care for Anthony. He's 63 and had a heart attack three years ago, brought on by stress," Tessa replied, anger burning bright in her eyes the longer she spoke. "They struggled to even put food on the table, to keep a roof over our heads. But the people who caused all of these problems were out having glamorous lives that they didn't deserve, not after what they did."

"And you took care of it," Kate said. "All that anger, all the frustration and rage, it all came out when Anthony died. You couldn't hold it in anymore, and you decided that payback was the only way you would ever feel better. So you started planning, researching these people and learning their patterns. You couldn't get Olivia at night, she didn't regularly go into the park, so you set her up. Lured her out into the dark, chased her down the footpath, and then stabbed her in the back."

"Did she scream for help, Tessa?" she asked, rising to her feet to lean over the table. "Did Levi try to fight you off, or did you hit him quick? You would want to wound him so it would be harder to get away. Can't have him making it back to the street and someone seeing you."

Stepping away from her chair, Kate circled around to the other side of the table, leaning down beside Tessa so that the woman had little choice but to lean away. With her gaze on Tessa, eyes glittering shards of ice that radiated her anger far more than yelling could do, she looked terrifying. "Cameron must have pissed you off," she said at her ear. "Levi's best friend at that summer camp, the guy that didn't stand up for himself, and just went along with the games. Sinning by silence with his perfect little restaurant and adorable family. How angry were you when he didn't come through the park last night? That you didn't get a chance to stab him in the back like you did the others?"

"I don't know what you're talking about," Tessa said, though it was far from convincing as it came out of her mouth.

"Oh, but you do," Castle replied, picking up the story that his wife was telling without missing a beat. "You stayed in those woods for hours, waiting and watching, looking for Cameron Warrington to come down that path you had seen him take so many times before. But last night? He took a cab. Hurried home to be with his sick son and you missed him."

"But you wanted to kill something, didn't you?" he asked, his voice growing quiet even when Tessa's breathing picked up, tongue darting out to wet her lips. "You had a taste for it now, and if you couldn't have Cameron, someone else, anyone else, would do. So you screamed, and when someone came running - when I came running - you tried to kill me."

Reaching up to adjust the sling on her arm, only to have the chain linking her hands halt her progress, Tessa gave a wince of pain, swallowing against it with a long breath. "I want a lawyer."

"Fine," Kate said, gathering up the photos and closing the file. "You can wait for one in lockup. Get used to the view, since you won't be seeing anything else for about 60 years."

"Hope you like concrete," Rick added, getting to his feet and following Kate out the door once a uniform opened it from the opposite side.

The plastic piece molded into a set of lethal-looking fangs slipped into his mouth easily enough, adding the final touch to the old-school Dracula costume that Rick had chosen for the party.

Working his mouth to loosen up the mouthpiece, he stepped over to the floor-length mirror in the bedroom, eyeing his handiwork with a critical eye. A dusting of white makeup to leave him ghostly pale, just a touch of eyeliner and mascara that he had only agreed to at the insistence of both his wife and daughter, and a sharp black suit with a blood-red vest and heavy black cape completed the look.

He had even asked Kate to use her eyeliner on his forehead, the tiny triangle that melded into the darkness of his hair giving a decent impression of a widow's peak with his slicked-back hairstyle. His wife had also gone the extra mile by putting in some work on his parting gift from Tessa, and covered up the cut on his neck with enough concealer and powder that it was hardly noticeable.

With no one in the bedroom to see, Rick gave a dramatic wave of the cape tied around his neck. As he had hoped, the fabric rippled and fell to cover his bent arm, keeping the lower half of his face in shadow for a brief moment.

One cock of his eyebrow, the slow lowering of the cape and a sinister smile, he put on his best Transylvanian accent: "I vant to suck your blood."

"I think that'll have to wait until later," Kate said as she moved into the room, the material of her long black dress and floor length cape swishing as she moved. "People are already here. I heard Alexis answer the door a few times."

Spinning to get a better look at her, he needed a moment to collect himself. The makeup Kate was wearing was severe, her cheekbones razor-sharp thanks to intense contour and highlighting of her skin. Blood-red lips and bold black eyeliner served to accentuate the cap that hid her hair completely and had two curving horns rising up at the sides of Kate's head.

"Maleficent?" he asked, trying not to stare as she hooked a thick black choker around her neck and flashed a smile that had him going just a little weak at the knees.

"I sent Alexis a text to try and find something, and she picked it out for me," she explained, reaching for the tall scepter that he hadn't noticed propped near the dresser. "Well, she got the horns and the staff. Martha brought me the cape from her studio, and I had the dress already."

Rick blinked at her for another moment before truly regaining his bearings, stumbling in Kate's wake into the office where his wife snagged the stuffed raven he had given her years ago at another version of his Halloween party from its perch on the bookshelf and attached the bird to the top of the staff with a pleased little smile.

His intentions were to cross the room and kiss her senseless, or at least long enough that Kate would scold him and have to go reapply her lipstick. Instead, Rick was forced to divert himself to the front door at a knock, walking through a living room blacked out and lit by candlelight, a rolling fog created by cleverly hidden dry ice machines covering the floor as his mother descended the staircase dressed as Frankenstein's Bride.

Her date, dressed as Frankenstein no less, stood on the other side of the door when Rick opened it. He didn't know the man's name, and there was no chance to ask with his mother swooping in to steal the guy from under his nose and drag him further into the loft.

With a shake of his head, Rick turned to take in the scene of a party in its infancy. Already, Hayley and Vikram had arrived, the two of them standing with Alexis in her Wednesday Addams getup and Kyle Hernandez dressed as Clark Kent with a Superman graphic t-shirt peeking out from under a standard button-down shirt.

Kate had migrated over to the Ryans, where Sarah Grace had fixed her with a dubious stare as she tugged on the delicate wings of her fairy costume. Her baby brother wasn't remotely fazed by Kate's costume, nestled in her lap and chewing happily on a teething ring made of tiny pumpkins while wearing his own Jack-o-lantern onesie. For just a moment Rick felt his heart skip and then fill with something indescribable at the sight.

All too soon Kate wouldn't need to snuggle with someone else's baby; she would have her own. His baby. Their baby.

And he was never gonna get over that.

"Castle, you're blocking the door."

Pulled from fantasizing over his wife and their unborn child, Rick spun to see Esposito wearing an old-fashioned pinstriped baseball uniform that was not at all what he would have expected.

Quickly stepping away from the entrance to the apartment, he flashed a grin at Espo, lightly slapping him on the shoulder. "Sorry, got caught up in the moment."

"Yeah, I saw you. If Beckett didn't have a baby in her arms it'd have been a little creepy," he teased.

Involved in their conversation, neither of them noticed the small figure that approached from the elevator in a white jumpsuit with a red ruffled collar. The clown's mask was appropriately creepy, with its teeth-baring grin and red button nose, and more than enough to send a shot of fear up Rick's spine when he caught sight of the clown just steps from Esposito.

"Espo…." he muttered, only an instant before the clown's hands closed around the cop's shoulder, turning him enough that Espo got a glimpse.

The scream he gave sounded far more girlish than anyone might have expected from Esposito, the detective pulling his arm away and darting into the loft by merely shoving Rick out of the way.

The clown stood its ground, bending double with a low chuckle that quickly grew into full-fledged laughter as the mask was pulled off, Lanie's hair tied into a neat braid and her face decorated with makeup that made for a cheerful clown rather than the horrific presence of the jester with the mask.

"Oh my God," Lanie snorted, still shaking with laughter. "That was too easy."

"Lanie!" Espo shouted as everyone else joined in with chuckles and giggles. "You know I hate clowns!"

"Which is exactly why I did it," the doctor replied, pausing to give Castle a quick hug before she tossed the mask in Esposito's direction and grinned when he flinched. "Happy Halloween!" she announced to the room at large, heading over to join Kate and Jenny on the couch as Rick closed the door and returned to the party.

Episode beta work by acertainzest and amtepe

Castle Season 9 is produced by Team Planet and the writing team of Castle Season 9. Executive Producer is encantadaa.

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