A/N Whelp, this chapter was originally posted with the story, but I took it down because I wasn't originally happy with the ending and liked it better without. But then every time I re-read it I just couldn't bear to not read the final chapter! So it didn't seem fair to withhold from all of you. Featuring minor editing - my original final chapter.

"Hurry, D!" Mikey bounced on his toes, scanning over the hallway again and again, nervously shifting as he waited for Donnie to finish 'doing machines'.

"I'm trying, Michaelangelo!" Donnie snapped, trying to reconnect the control panel's wires.

Mikey nodded, and was quiet for a whole 30 seconds. "Man, who woulda thought the Krang had another portal, right? I mean, I was so not expecting, like. Invading Krang. I thought we were done with that, huh?"

No response, so Mikey kept guarding the hallway in case of visitors. "I sure hope you finish that soon, bro. I'll feel a lot better when you're done. I mean, I totally thought we were done fighting the Krang, so I'll be glad when we're done the second time. Right, Donnie?"

Still no response, so Mikey turned around to get a good look at Donnie. Don's hands were shoved into his head and he slumped against the wall, gasping silently and trembling.

"Donnie?" Mikey dashed to Don's side, falling to his knees beside his brother. His hands moved to hover uncertainly over Don's side. "Are you okay, bro? Didja get shot?"

"N-no… I'm okay. Just keep lookout… I'll get back to it…" Donnie tried to push himself up but collapsed, only Mikey's arms keeping him from hitting the floor.

"You're not good, D. Something's wrong, what is it?" Mikey held Donnie in some semblance of upright, and Donnie gripped his forearms, but tried to push backward.

"L-let go of me. I'm alright, I'll be okay in a second-" Donnie thrashed, but Mikey held firm.

"Donnie I-" Mikey cried out as he and Donnie jolted with a painfully familiar biting energy.

Mikey managed to release his brother and spin around glancing all over for anyone who could have possibly have attacked them. "Wh...whaaa?"

Mikey threw his gaze back to Donnie, but Donnie's eyes were rooted on the ground and he trembled, energy visibly crackling in tiny spurts over his body.

Mikey's voice was tiny, young, and terrified. "..Donnie?"

Donnie refused to look up, trembling and gritting his teeth until the electricity faded. He pushed himself back up to the panel. "Just keep guard, Mikey. It'll… it'll all be okay."

"LEO!" Leo turned in time to catch Mikey full-on bodyslamming him into a hug, tears leaking from the corners of his eyes. Leo felt his heart petrify as he seized up, fingers numbing.

"Mikey? Mikey, what's wrong? Where's Donnie? Is… is he-?"

Mikey shook his head against Leo's neck, still clutching his brother's shoulders for comfort. "N-n-no but he's… Leo!"

Leo clutched Mikey to his chest and exchanged frantic glances with Raph, who whipped out his T-phone to call Donnie.

"Mikey, you gotta tell me, where's Donnie?"

"He's comin', but he's got… he's…"

"Mikey, you aren't making sense!" Leo cried, brushing a hand over Mikey's head to calm him down, sheathing his katana. "Just calm down and tell me-"

"Here I am!" Donnie dashed out of the hallway, bo in hand. "Let's talk when we get home?"

Leo and Raph gave simultaneous sighs of relief that Donnie at least appeared unharmed, and Raph moved forward to ensure that Donnie truly was in one piece.

"Never do that again," Raph ordered roughly, slugging Don's shoulder.

Donnie managed a tight smile. "Sounds like a plan."

The four brothers finally tramped into their living room, Mikey having fallen silent long ago. Raph whirled around, glaring at Don and Mikey. Don passed a hand over his eyes as he prepared for the completely inevitable confrontation.

"Alright, you two, spit it out. What scared Mikey so bad that he had to come scare us half out of our shells?"

Donnie drew himself up. "You guys should all probably sit down…"

"He felt like April was disintegrating him again! I saw it and I touched him and it was totally the same energy and everything!"

Donnie glared at Mikey, as Leo and Raph whirled to face him.

"...You still want to sit down."

"No, I don't think we do," Leo challenged, striding up to his younger brother.

"Everyone, please just sit down!" Donnie stalked away to drag a chair in front of the couch and flopped into it. "We can get started then."

Leo and Raph hesitated, but Mikey stalked forward, plopping onto the couch and folding his arms. Leo followed, and Raph trailed after him. "We're all sitting down," Leo said, glaring at Donnie. "Now what?"

Donnie let out a breath, placing his hands on his knees. "Okay. It's about time I told you anyway. You know when Zanaron dispersed my molecules over the city, and then April put me back together. Well, after that I've been having… attacks. I think…" Donnie fidgeted, then stood up to pace.

"I think I wasn't supposed to come back. Like Master Splinter wasn't supposed to come back."

Mikey whimpered and leaned into Leo, who slipped an arm around his shell. Donnie turned back to face his siblings for a moment.

"I'm not supposed to be alive right now. And every moment that I am…" he made a vague gesture, "this… energy tries harder to make me not be. Basically, it's quantum mechanics and… stuff, but… I keep having these attacks, where the energy comes back."

Donnie walked back to the chair and fell into it. "I was always able to postpone them throughout missions before and have them at night but I guess… it's too advanced, now."

Donnie glanced up, tears hanging in the corners of his eyes. "I've done the tests, to see how long I think I have left-"

Mikey dashed forward clinging to Donnie with all his strength. Donnie buried his face in his little brother; hugging him back, choking out: "I think I have eight years."

Leo and Raph joined the pile and somehow Donnie ended up tugged to the floor. "Why didn't you tell us?" Leo whispered.

Donnie sniffed. "I didn't want you to worry. I thought I might be able to...fix it, but I haven't found anything, I don't think there's anything I can do… I'm sorry, I'm really sorry."

Raph bumped Donnie's cheek with his snout. "Don't be dumb, genius. And don't keep secrets, either. We're gonna fix ya up. Eight years is plenty long to figure something out."

Donnie ducked his head and bit his lip as tears leaked from his eyes.

Leo pressed a hand to Donnie's plastron, looking deep into his brother's eyes. "Don't give up, Donnie. Raph's right: the universe is a big place, and we'll look under every galaxy in the universe to find a cure for you." Leo grabbed the back of Donnie's neck and bumped noses with his lanky brother. "You'll be alright."

Donnie closed his eyes and tried to believe it.

A/N In case you want my personal headcannon on what happens to Donnie - he lives longer than 8 years but still dies young, about 15 years from the end of this fic. Do with that what you will.