Summary: It has been two weeks since Donatello first locked himself away in his lab, busy on his latest 'project', and Leo is starting to worry. Hoping to help his brother, Leo asks Don if he needs any help. However, Leo soon finds himself restrained under the hands of his brother, and as time passes, Leo has to wonder exactly what kind of scientist Donatello really is…

Disclaimer: All rights belong to their respective owners.

A/n: The idea for this story was given to me by the talented Amonraphoenix. I am also lucky enough to have had this story edited by Amonraphoenixas well. This project has been in the works for some months now, and I have only now been able to upload it due to a heavy study load. I hope you all enjoy this one-shot, and reviews are most certainty welcome and appreciated. When my work load dies down a little, I have plenty more wonderfully dark ideas given to me by Amonraphoenix that I hope to share with you all.

Mad Scientist

"Everybody's a mad scientist, and life is their lab. We're all trying to experiment to find a way to live, to solve problems, to fend off madness and chaos." ~David Cronenberg

Leonardo stared at the closed door with a frustrated sigh. His younger brother, Donatello, had locked himself in his room, as he worked madly on another of his many 'projects'. It had been two weeks since Donnie sealed himself in his lab and Leo hadn't seen his genius brother leave the room once. He knew that Donnie was very passionate about his research and his projects, and he had learnt from prior experience that when the genius turtle was in one of his 'crazy scientist' moods, it was best to leave him alone until he snapped out of it. So Leo had been lax with training, and excusing Donnie from patrols, hoping his brother would soon emerge from his lab.

However, Leo was starting to lose his patience, and was becoming increasingly worried about his brother. He wondered how often Donnie had been sleeping- if at all- and how regularly he was having meals. Leo hadn't seen Donnie enter the kitchen once since he had locked himself away in his study, not even for a cup of coffee, or 'brain juice', as Donnie would call it; Leo suspected he must have a source of coffee buried somewhere inside the chaos that was his lab.

Leo decided he would make his brother breakfast and go see him for himself. He knew Donnie was stubborn when it came to his research and projects, but Leo also knew he would listen to Leo if he pressed him hard enough. Maybe he could even offer Donnie some help, if it would speed up the process of Donnie returning to training and patrolling, along with a normal eating and sleeping pattern.

Walking purposefully into the kitchen, Leo scanned the cupboards with a slight frown, taking stock of the various food items. Leo was a master of Nin-jit-sui, and had mastered the twin katanna's, and was able to successfully find peace of mind whenever he meditated. However, for all of his training and skills, Leonardo was useless when it came to cooking even the simplest dishes. Deciding to play it safe, Leo took two slices of bread and put them in the toaster. Surely he could make toast. While the toast was toasting, Leo filled a kettle with water and set it on the stove to heat, Leo scooped a spoonful of dark instant coffee beans into a coffee mug, and placed it on a tray next to a plate for the toast. Grabbing an apple from the fruit basket, Leo also placed it on the tray before grabbing a small bowel and filling it with one of Splinter's muesli cereals. The odour of burning bread suddenly filled Leo's nostrils. Cursing, he ran over to the toaster and pressed the little button on the side, making the toast pop. The toast was very well done, the edges starting to turn black. Leo cringed, but hoped that Don wouldn't notice his failed attempt if he slathered the toast in superfluous amount of peanut butter.

Having placed everything on the tray, Leo smiled at his effort, and picked up the tray, carrying it to Donnie's lab. The door was closed and no light shone out from under the door. Leo knew that was normal. Donnie had always preferred to work in the dark, his many computer monitors often the only source of light for the genius to work by.

Shifting the tray, Leo knocked loudly on the door. "Hey, Donnie, it's me, I brought you breakfast!" Leo called out loudly.

There was the sound of rustling inside before the door creaked opened, and a very disheveled Donatello appeared in the doorway.

"Hey, Leo," he said around a wide yawn, stretching his arms high above his head. "What's up?"

"I thought you could do with some breakfast," Leo said cheerfully, presenting Donnie with the tray of food. "You need to keep your strength up."

"Thanks, Leo," Don smiled gratefully, taking the tray from Leo and turning back into his dark lab. "I've been pretty busy and haven't thought much about food."

"I can tell," Leo said, following his brother into the dimly lit room.

Paper was scattered over every available surface. Textbooks were piled high in the corner and the glow from five computer monitors bathed the small room in an eerie light.

Don set the tray down on the desk before he plopped down onto his computer chair and took a long sip of the coffee Leo had prepared him. Donnie sighed appreciatively in pleasure from the hot drink.

"So, what are you working on?" Leo asked, perching himself on one of Don's many workbenches. He wanted to stick around to make sure Donnie actually ate something besides coffee.

"I've been working on human and turtle anatomy," Don explained, taking a bite out of the burnt toast. "I've been trying to improve my medical knowledge of our unique anatomy and I've found some interesting stuff I didn't know before. Hopefully this extra study will help me to understand how the two anatomies merged because of the mutation we went through."

Leo nodded in approval. "That's great, Donnie," he offered his brother an encouraging smile. "Do you need help with anything? I'm not very good at all this medical stuff but if you need a hand with anything I'll happily help as best I can."

"Actually," Donnie said, abruptly getting to his feet and striding over to one of his workbenches. "I could use your help with something," he said, opening one of the desk's drawers and pulling something out.

Leo was a little surprised that Donnie was accepting his offer to help. Usually there wasn't a lot he or his brothers could do to help their genius brother. "What do you need me to do?" Leo asked politely, sitting a little straighter on the desk.

"Just keep perfectly still for me," Don said with a devious smile as he walked back over to Leo.

Leo felt a sudden prick in his neck, and the next second his world started to turn blurry. He felt his body start to become numb and his vision wavered. "What…happen?" Leo slurred in fear and confusion, his tongue feeling heavy in his mouth. He could vaguely make out Don's blurry form above him.

"You're helping…" Don's voice echoed eerily around the room before everything went dark.

Leo woke to a sudden brightness. Blinking his eyes, Leo tried to get use to the harsh light. He felt dizzy and disoriented, and his head pounded with the beginning of what felt like the beginnings of a migraine. Blinking his eyes open cautiously, Leo took a moment to remember where he was. The familiar backdrop of Don's lab came slowly into focus. His memory soon caught up. He had come to visit his brother to make sure he ate something. Don had accepted the offered food with a smile and had started eating the burnt toast. Everything after that was…fuzzy, like a dream. The more he tried to remember the harder it was to try and focus.

Still blinking in the unnatural brightness of the room, Leo realised that he was lying down. Maybe he had fainted? That would explain why he was lying down in Don's lab with a sore head.

Trying to shake off the fog that clung to his mind like early morning mist, Leo tried to push himself into a sitting position. Except he couldn't move. With a jerk of his head Leo realised that his arms and legs were strapped to what appeared to be a hospital gurney. Thick leather straps had him buckled firmly in place.

"What the hell?" Leo muttered, trying to tug his limbs free.

"Ah, you're awake," a voice said from the shadows of the room.

Leo squinted as Don slowly approached him, a gentle smile on his face, though there didn't appear to be any warmth in it.

"What's going on, Donnie?" Leo demanded, his throat feeling like sandpaper.

"You offered to help me with my research, remember?" Don prodded, standing beside Leo with his arms crossed behind his back.

Leo blinked, suddenly remembering. "Why am I strapped down, though? Is this part of your research?" Leo asked in confusion.

"You could say that," Don said, idly tapping his chin. "It felt like my research wasn't going anywhere, so of course I jumped at the opportunity for help."

That's when Leo realised that Don was dressed in blue surgical scrubs, a mask pulled down over his chin.

"What…what exactly do you need me to do?" Leo swallowed, a hollow feeling in his gut.

"I told you I need to improve my medical knowledge on our anatomy," Don replied excitedly with a widening grin. "What better way to do that than observe it first hand?"

"I…I don't understand," Leo frowned; worry starting to worm its way through his chest.

"I am going to improve my medical knowledge by observing you," Don explained slowly, as if he were explaining something to a toddler. When Leo still looked at him in confusion, Donnie sighed dramatically. "I'm going to dissect you, Leo."

Leo stared at his brother in horror and confusion, not sure if this was all an elaborate prank. He struggled against his bonds. "You can't be serious?"

"Oh, but I am," Don said quietly, staring down at Leo like he was a new species of insect to be pulled apart. "Deadly serious."

Leo tried to suppress a shiver as his brother abruptly turned away from him to rummage through the various tools Leo only just noticed set out on a table beside him. There were many tools Leo had never seen before, and some he had; needles of various sizes, saws, calipers…

Don turned back to face his brother, a long needle filled with bluish liquid in his hand. "Now, this won't hurt a bit," Don said softly with a reassuring smile, before promptly inserting the needle into Leo's arm.

"What is that?" Leo asked in panic, trying futilely to twist out of his restraints.

"It's a little cocktail I cooked up," Don explained, setting the needle back down on the table before pulling on a pair of customize surgical gloves. "You should feel the effects start to kick in soon. It will keep you conscious but numb your body, so you shouldn't feel a thing."

"If this is a joke, it's gone far enough," Leo barked firmly, trying to sound as in-control and 'leader-ish' as possible.

"Science is no joke," Don said with a serious face. "I assure you, Leo, this is no joke, I am quite serious."

Leo swallowed, staring up in shock at his brother. This had to be a nightmare. This whole thing had to be one big night terror. Leo knew his brother would never do this to him; he just needed to wake up.

"Shall we begin?" Don asked calmly, clapping his hands together. Turning back to the table laid out with instruments, Don picked up a large circular saw. "First I need to make an incision in your plastron," Don explained evenly, as if he were explaining something as simple as current weather.

Leo stared in horror at the wicked looking saw in Don's hands. He couldn't believe this was happening.

Our carapace and plastron is covered in a thick layer of keratin over hard dermal bones," Don continued to explain, positioning the saw over Leo's plastron. "This helps to give it extra strength and flexibility."

Don turned the saw on and Leo cringed back as the whirring sound of the blade filled his eyes and ears. "Now, just try to relax," Don reminded him. "With the injection I gave you, you should only feel a slight tickle and some pressure."

Leo could do nothing but stare in horror as the saw descended on his prone body, changing into a high-pitched squealing sound as it made contact with his plastron plates. Leo closed his eyes and gasped, ready to scream in agony. But the pain he expected did not come. He knew what was happening, and saw Don moving the saw expertly across his chest as he carefully cut each of his plastron scutes from his body, but he was unable to feel anything.

This is wrong, this is so wrong, Leo thought wildly to himself. He was still convinced this was just a messed-up nightmare that felt entirely too real, but a dream nevertheless.

Leo forced himself to stare at the ceiling. He couldn't look at his brother, couldn't look at the monster beneath his brother's skin. And he couldn't look at himself either. Although he couldn't feel any pain, Leo knew if he saw what was happening, he would throw up or pass out cold.

"It's interesting, the differences between turtle and human," Don said, talking as normally as one would talk at a breakfast table. Leo made the mistake of rolling his head to the side to look at his brother. Dark red blood coated Don's hands and splattered against his once blue surgical scrubs. Leo blanched and forced himself to quickly look away, all the while repeating to himself that this was all a bad dream and he would soon wake up in his own bed, whole and intact.

"A turtle's brain is highly developed with sight and smell senses, which is why we can see more easily in the dark than an average human," Don continued. "Turtles can also withstand longer periods of oxygen deprivation than humans, which is why we can hold our breath a lot longer," Donnie continued.

A strange sensation flowed through Leo, and he looked up to see Donnie holding what appeared to be a bloodied chunk of meat.

"This is one of your kidneys," Don explained, seeing Leo's horrified expression. "Fascinating, its very similar to a human." Donnie exclaimed as he examined the organ.

Leo felt bile rise in his throat and forced himself to close his eyes. As he faintly felt Donnie's hands move around his intestines before he started to remove them. Leo felt himself go pale at the sight of the long pale pink organ was removed with a squelching sound before being plopped in a large bucket.

Wake up, wake up… WAKE UP! Leo screamed in his head.

"Now, don't be alarmed if you hear cracking," Don continued calmly, like he wasn't covered in his brother's blood. "I'm going to examine your heart and lungs, but to do so I need to break several ribs to access it. You might feel an odd pinching sensation, but you shouldn't experience too much pain."

Leo watched in frozen horror as Don's hand disappeared inside his chest, followed by the sound of a twigs snapping. Leo turned his head to the side and vomited down the side of the medical gurney.

"I know this must be unpleasant for you, but it will be over before you know it," Don said cheerily.

The cracking noises continued, and with each agonizing minute that passed, Leo wasn't so sure if he were dreaming, or if this was actually happening to him.

"Another interesting difference; turtles only have a three-chamber heart, instead of a four-chamber heart. I am curious to see what our mutation has done to your heart."

"Why are you doing this?" Leo whispered, as tears slid down his cheek.

Don paused and looked at his brother with confusion. "I told you why I'm doing this, to help broaden my understanding of our unique anatomy."

"I'm your brother! Please Donnie, stop this, this isn't you!" Leo beseeched, forcing his brother to meet his pleading eyes.

Don frowned down at his brother in confusion. "You offered to help me, Leo. This is me, this has always been me. I have always had an unquenchable thirst for knowledge. Besides, this will all be over soon."

Leo suddenly felt very dizzy and very…light, like he was no longer attached to his body. What little feeling he had left in his body disappeared, and his vision started to waver.

"Four-chambers!" Don cried out enthusiastically, his voice starting to fade.

With Leo's final breath he saw his still beating heart clutched in his brother's hand. Don smiled proudly down at him before everything went black.

Leo bolted awake, his body coated in a cold sweat and his heart racing wildly in his chest. He was in his room, in his bed, safe and sound. It had only been a horrific, far too realistic)nightmare after all.

Forcing himself to take slow, deep breaths, Leo shakily got to his feet and tried to shake the fragments of the nightmare from his mind.

It was just a dream.

Glancing at his bedside clock, Leo realised that he had slept-in longer than he usually did. The bright red digits read 7:04 am. Trying to regain some composure, Leo made his way down the stairs and into the kitchen. He could see the door to Don's lab closed, and no light shone beneath.

Maybe he's finally decided to take a break from all his studying, Leo thought to himself as he made his way over to the door. He stopped and hesitantly raised his hand to knock, feeling a sense of dread wash over him.

Stop it, it was just a dream, Leo chastised himself and knocked loudly.

There was the sound of rustling inside before the door opened, and a very disheveled and half asleep Donatello appeared in the doorway.

"Hey, Leo," he said around a wide yawn, stretching his arms high above his head. "What's up?"

"I…I wanted to see how you were," Leo stammered, hit with a sudden wave of dajuvu. "You've been locked away for a while now."

"I've been pretty busy," Don admitted sheepishly, beckoning for Leo to follow him into the room.

"I can tell," Leo said, following Donnie into the dimly lit room.

Paper was scattered over every available surface. Textbooks were piled high in the corner and the glow from three computer monitors bathed the small room in an eerie light.

"So, what are you working on?" Leo asked, perching himself on one of Don's many workbenches. He couldn't shake the eerie sense of Dejavu he felt as soon as he entered the room.

It's just Donnie, your brother… relax.

"I've been working on human and turtle anatomy," Don explained. "I've been trying to improve my medical records, and I've found some interesting stuff I didn't know before. Hopefully this extra study will help me to understand our unique bodies."

Leo froze his whole body filling with an ice-cold dread.

"Actually," Donnie said, abruptly getting to his feet and striding over to one of his workbenches. "I could use your help," he said, opening one of the desk's drawers and pulling something out.

Oh god, please no!

"Just keep perfectly still for me…"