VERY SLIGHT SPOILERS: 'New girl in town'

It was a nice summer day. The sun was shining, not a cloud to be seen, not much traffic (considering you live in New York, anyway). But under the ground, things weren't so peaceful.
In the lair of the four brothers was a huge fight going on.
Raph VS Leo. The usual. Mikey and Donnie were just sitting on the couch, waiting for it to end to they could start their sparring session.

Master Splinter had left for two days and had left Leo in charge. Mikey and Donnie were fine with that. Raph… not so much.
"Why did he leave you in charge?!", Raph yelled "I could do way better than you!"
"Oh yeah?!", Leo yelled back "I remember when I left you in charge! Mikey almost got killed! If Donnie hadn't been there, all of you would have been goners!"
Donnie sighed and looked at Mikey. They both remembered the fight with snakeweed a couple of months ago. Raph had a nervous breakdown and Donnie had gotten them out of there back to safety.

"Guys", Donnie tried to interfere "Can we please leave me out of this and just start sparring?"
"Don, you always want to get out of a fight without actually fighting!", Raph replied "For once, say what you think for real!"
"Raph, you know Donnie never inferteres when we're talking like this!", Leo yelled at Raph "He's too much of a coward to do that! The only time he's brave if when he's working on one of projects! And only because there's a 95% chance that they will blow up and kill the entire population of New York! And that even turns him into the worst ninja imaginable! "

SLAP

Raph and Mikey just stood there with their mouths open and eyes who could fall out of their head any moment, watching Leo lying on the ground. On his left cheek was a red mark, shaped exactly like Donnie's hand. Donnie himself had moved with a speed nobody could have expected from the genius and had slapped his brother!
Leo just lay there with his hand on his cheek. When he looked up, he looked straight into the eyes of Donnie. Straight into the dark brown eyes that normally held so much care and calmness. Now, there only was anger. Much like Raph, actually.

Leo pulled himself into a sitting position and thought about what he had just said to his brother.
Too much of a coward, they will blow up, worst ninja imaginable...
The gravity of his words started to dawn on him.
Leo bit his lower lip as he looked up again: "Donnie, I-" But he never even got the chance to finish his sentence.

"I know I'll never be good enough for you, Leonardo. But I just hoped you could accept me the way I am. But clearly, I'm not as smart as I thought I was, because I could never have seen this coming…"
After that, he just turned around and walked away. He didn't run, he didn't even jump over their entrance! He just walked, like he gave the others a chance to convince him to stay. But the others were to shocked to even move.

When he was just out of sight, Donnie stopped and listened if anybody was coming. There wasn't a sound to be heard. He took a deep breath and sighed: "Fine. If that's the way you want things to be, it's hardly fair to argue…". And nobody saw the single tear rolling down his cheek.

Back at the lair, Raph had finally gotten over the shock and pulled Leo back to his feet: "You okay, bro? That was a pretty hard slap!"
But Leo didn't answer. All he did was sigh: "I didn't mean it, Donnie… He knows that, right?"
He turned to Raph and Mikey when he said that. His two younger brothers looked at each other, but didn't say anything.

After a while, Mikey spoke up: "I don't know, Leo. He looked pretty angry…"
Raph shook his head: "That wasn't just angry. That was anger that concealed pain. Believe me, I should know! He didn't want to show how much you hurt him, so he slapped you instead."
"I have to find him!", Leo said "I have to make this up to him!" "I'll come with you", Mikey said. "And I'll stay here, in case he would come back", Raph added.

Leo and Mikey took off and yelled Don's name through the entire sewer system which was known to them (which was a huge part!). But no Donatello to be found.
"We will have to face it…", Leo finally said when they were back home "Donnie is gone…"

Author's note: Hi! :) Hope you liked it! Originally, this was supposed to be a one-shot, but turned out a little longer than I was expecting… Anyway, review and let me know if you would like me to continue this!

And, last but certainly(!) not least: enjoy your summer vacation!... :D