AN: Thank you so much to everyone who showed interest in this fic! Let's see what Donatello will do now…


Which One?


When Donatello came back to the lair, he noted with deep relief that none of his brothers had noticed his absence. Michelangelo was still in front of the TV, and from the sounds coming from the dojo, Leonardo and Raphael were training together. His father was nowhere to be seen - probably meditating in his room.

Donatello slipped inside his lab and closed the doors behind him, before leaning against one of the panels. He breathed deeply, trying not to panic. So far, so good.

For a brief second, he wished that the last two hours had never happened, that he was still safe inside his home, that Irma had never contacted him.

However, wishful thinking wasn't going to help, and he had a brother to save. Preferably without killing himself in the process.

It was time to examine the vial that Irma had given him, and its content. Should he lock himself in his lab to do so? That way, he was sure that he would have the time to hide anything suspicious if somebody tried to enter. But it would also make his brothers very curious, and of course Mikey would stop at nothing to know what he was doing. Not that Raphael and Leonardo wouldn't want to know too. On the other end, it wouldn't be the first time that he went to such lengths to have some peace and quiet.

Or he could keep the door unlocked and pretend that it was an experiment of some kind. It wouldn't even be wrong. But what if Mikey played with it? His brother loved to interfere with Donatello's most dangerous experiments.

And this time, he was unable to predict just how dangerous it was.

Donatello shuddered at the thought of Mikey accidentally taking some of the vial's content. No, he couldn't take that risk.

Having made his decision, he locked the door and sat at his desk, switching on a powerful lamp. He grabbed a notebook, took the vial and examined it. It was electric blue, and more viscous than water. Going under his self-made extractor in case it released a poisonous smell, he opened it.

Nothing happened. Good, it meant that it didn't react with oxygen and…

Somebody banged on the lab doors. "Donniiiiiie!"

Donatello quickly recorked the vial and hid it in his belt, but he didn't open the door. "Yes, Mikey?"

"Donnie, I'm bored. Help me!"

Donatello winced. He had hoped that his brother would be watching TV for another hour at least, but Michelangelo seemed to have a sixth sense. It was as if he knew when Donatello didn't want to be disturbed, and made a point of doing just that.

Then he remembered that maybe Michelangelo was now in mortal danger, and wondered anxiously if Irma's detonator was the only way of triggering the bomb, or if strong emotions could activate it too. Maybe he was worsening things by upsetting his brother?

The banging renewed. "Donnie!"

Taking his decision, Donatello opened the door and Michelangelo burst inside, glaring at him.

"You know I don't like when you lock yourself up," he moaned. "It makes me believe that I'm not welcome."

Donatello pointed a finger up, indicating that he was about to share invaluable wisdom and hoping that his brother couldn't tell how fast his heart was beating, or how worried about him he was.

"You see, Mikey, the whole purpose of locking a door means that you don't want to be disturbed. So basically, nobody is welcome."

Michelangelo stuck his tongue out at him before swirling across the room. Donatello ran behind him to make sure that he wasn't going to accidentally knock over precious scientific equipment. Like that microscope, here in the corner.

"Oops!"

"Be careful, Mikey, this baby is delicate!" Donatello half-heartedly scolded him. Could an impact also trigger the bomb? No, probably not. Irma would have warned him if it did, she wouldn't want her experiment to stop before it had even begun, would she?

Still, he would feel better if his brother settled down and did a nice, quiet activity. Like reading. Or meditating.

Well, it was Michelangelo, so the first possibility was more likely.

"Don't you have a new comic book to read?"

Michelangelo shook his head. "Nope. And I don't want to read the old ones, I want to hang out with you."

His grin was so wide that a wave of guilt engulfed Donatello. But how was he supposed to figure things out with the vial and Irma if he didn't have time to think?

He hadn't even thoroughly checked the lair for hidden cameras or microphones. He suspected that Irma might have left a few of them. She was too well informed about their whereabouts.

He wondered if Irma would be angry if he removed them. She hadn't forbidden him to do so. Her instructions had been crystal clear: she wanted him to take the vial's content, one drop at a time, and to report to her every day with his feelings and symptoms - if any. Or one of his brothers would die.

He didn't doubt that she had indeed managed to implant a bomb inside one of them - she had described the process in great detail to Donatello, as much as leaving the syringe she had used in his very own lab. He didn't know if she had been inside the lair or sent a drone, but the fact was that he had found it behind his desk, like she had described it.

He had searched it for DNA traces to know if it was Michelangelo, Raphael or Leonardo who was carrying the bomb, but hadn't found anything. Of course, he could check each of his brothers in turn, and he would have his answer - except it would trigger the device and kill them.

Donatello tried not to think about what Irma's mixture was going to do to his body. Was it some sort of mutagen? Or retromutagen? Or something else entirely? Or…

"Sewers to Donnie. You're not paying any attention to me!"

Michelangelo's pouting voice snapped him out of his thoughts.

"Uh, sorry, Mikey."

Michelangelo let out a deep, disappointed sigh.

"It's not fun if you don't listen at all, Dee. You should focus more."

Donatello gaped as Michelangelo patted his shoulder. "Don't worry. It'll come with practice."

Right before he left, having apparently understood that his brother really needed his peace and quiet to sort his troubled thoughts, Michelangelo turned around to point a finger at Donatello.

"I'll be back," he whispered.

Donatello kept watching the doors for a long time after Michelangelo had closed them behind him, his heart aching. Michelangelo, his so lively and ready-to-help brother.

Was it him?


Donatello should have known that his tranquility wouldn't last long. He had barely evaluated the density of the foreign liquid and written down the result in his notebook when he heard a polite knock at his doors.

"Donnie?"

Raphael. He rarely disturbed him in his lab, so it had to be something important. Was he feeling strange because he now had a Kraang-designed foreign body under his skin?

Donatello ran to the doors and unlocked them.

"Yes, Raph?" he exclaimed, leaning forward to take a closer look at him. Was his skin a different color? Paler, maybe?

Raphael took a surprised step back. "What's with you?" he protested.

"Uh, sorry." Donatello did his best to hide his embarrassment and concern as he straightened up.

Raphael crossed his arms. "I just wanted to tell you that Casey's dad is getting rid of his old satellite dish. He wants to know if you're interested."

Donatello breathed deeply. He got along better with Casey these days. During their time at Northampton, he had realized that they had more in common than he thought - apart from the fact that they were both in love with the same girl, that was. They shared a passion for mechanics, and Casey had helped him more often than not with his engineering projects… And he was always on the lookout for spare parts.

"Yes, thank you. It's nice from him."

Raphael nodded. "Alright. I'll tell him to save it for you." Tilting his head, he looked at Donatello's hands. "What are you working on? Retromutagen again? I thought you didn't know how Mikey had altered your last mixture."

Donatello realized with horror that he had his notebook in hand, open and showing a detailed sketch of the vial as much as his latest calculations. In his eagerness to check on Raphael, he had forgotten to hide it. Worse, the vial itself was still on his desk…

His eyes widened in horror. A plan. He needed a plan to distract Raphael's attention.

"It's… it's…" He wedged the notebook between his elbow and his shell and intertwined his fingers. Time to bring out the big guns. "I'm in the middle of designating a new process for following the chemical interactions of biological compounds, as well as comparing the relative merits of Newton's principles versus Einstein's relativity theory when measuring the mass of an object that's…

Raphael hastily threw up his hands. "My bad. Sorry I asked."

Donatello tried not to look too smug. It worked every time.

Raphael shook his head. "Well, I'll leave you to your work, then." He took a last look at Donatello. "And take some rest, Donnie, you look terrible."

Donatello nodded, watching Raphael depart. He had no doubt that he was looking terrible. Being blackmailed by aliens and threatened with the death of a beloved one could do that to you, not that he would have told Raphael that.

Raphael, so caring in spite of his declared toughness.

Was it him?


Donatello was completely unsurprised when he heard somebody knock at his door for the third time. Some days, it seemed that his brothers spread the word to prevent him from achieving anything.

"Donnie, do you have a minute?"

Donatello quickly hid the vial and his notebook and opened the door, resigned.

"Sure, Leo. Come in."

He discreetly watched his brother for signs that he might carry a bomb, however tiny. Leonardo looked tired, but after everything they had gone through in the previous weeks - them saving New York, again, repelling the Kraang, again, and bringing back the citizens from Dimension X - it wasn't so surprising. Was his knee aching again? No, his brother had assured them that it was completely healed.

Leonardo raised an eye ridge. "Uh, Donnie?"

Donatello realized that his inspection hadn't gone unnoticed and coughed.

"Sorry. What did you want to say?"

"I would like to make sure that the Kraang left nothing behind them in New York," Leonardo began. "No portals, no technology, nothing. I never want to see their faces again."

Donatello bit his tongue to avoid telling his brother that it was a good idea, although it might be a little late.

"April will help us," Leonardo went on. "She thinks she can detect alien technology." He smiled. "And if there are any portals left, I trust Mikey to find them." He shook his head. "Anyways. Do you have anything that could help? We have April's mind skills and Mikey's intuition, and I would like to add your crazy inventions to the mix. I don't want to miss anything."

Donatello bit his tongue harder. A fully functional Irma lurking in the sewers probably counted as 'anything', but he couldn't tell Leonardo that. After a few seconds, though, he realized that his brother was waiting for an answer and carefully opened his mouth to talk.

"I…I…"

Leonardo tilted his head. "Yes?"

"I have my old mutagen-detector," Donatello finally said. "It would need a few adjustments, but with a little work…"

"That would be perfect." Leonardo nodded. "Do you think it'll be ready for tonight's patrol?"

"Tonight's patrol is in three hours." Donatello couldn't help glaring at his brother. Did he think it was that easy? He would have to rework the structure, and maybe weld a few of the spare parts he had salvaged from their last fight with the Kraang. He could already picture the drawing in his head - but it would take him most of these three hours, hours he needed to work on something entirely different.

Leonardo must have understood his brother's reticence, because he looked sheepish. "Yeah, I guess it's not much time."

"No kidding," Donatello muttered.

"Do your best, okay? At the very least, it'll still detect mutagen. Everything else is a bonus."

Donatello nodded. There was nothing else he could do - Leonardo was right, it was best to check if the Kraang had left anything behind. In any other situation, it would have become his number one priority.

"I'll try."

"Thanks, Donnie. You're the best."

Donatello managed a poor smile, a smile that disappeared as soon as his brother left the lab.

Was it Leonardo? Attacking the leader would have been a clever move. In one stroke, Irma made sure that Donatello would cooperate, and that they wouldn't be able to retaliate easily if anything went awry.

Donatello let himself sink in his chair and took his head in his hands. He couldn't be sure why Irma hadn't told him which one of his brothers it was - he suspected that it was a petty revenge on her part for literally reducing her to pieces - but the uncertainty was driving him crazy.

Not that it mattered in the end. For each and any of them, he would have gone to hell and back. Hopefully back.

With a deep sigh, Donatello straightened up. He had no time to lose if he wanted to send his first report to Irma before they went out for patrol. Feeling numb, he took the vial -

opened it -

collected a single drop with a pipette -

and swallowed it.