A/N: I have no excuse for this story. Hopefully, someone will enjoy it anyhow.

Charlie looked up at his class. They stretched above him in the auditorium, playing with their pens and doodling on paper and staring at the clock, waiting for class to end. Some, though, were watching with interest. That was heartening. Charlie cleared his throat, smiling shyly. "It's like bumper cars," he said, his eyes glazing over a little with the effort of translating his internal vision into something undergraduates could understand. "There's a defined area in which each car can move, and as they move, they interact with each other. They hit into each other, they touch, and they transfer kinetic energy. With the equations-"

But the class wasn't going to find out what bumper cars had to do with the math of fluid dynamics. The gunshots were shockingly loud in the enclosed space, the sound bouncing around the walls despite the blocks of sound-absorbing cloth. Charlie's body jerked as the bullets hit into him, and red blood bloomed on the white fabric of his shirt. Charlie looked up, confusion clear on his face. He staggered back one step, and fell.

The classroom erupted into chaos.

Charlie had seen the figure in the gray hoodie come into his class. The newcomer was hunched over- hands in pockets, face obscured below the hood. They'd slipped into the back row, and he'd thought nothing more of it. He had something like 80 students in his Beginning Applied Mathematics course, and he didn't even try to know them all.

He'd noticed, idly, that the newcomer in the hoodie was getting up in the middle of his lecture. He always found that irritating, but really, if students were going to skip class it was on their own heads. They were mostly at least nominally adults, and they'd soon figure out on their own that skipping class was a bad idea.

He was no longer paying attention when the hooded figure moved to the top of the aisle and leveled a gun at him. His mind's eye was filled with bumper cars and the equations of kinetic transfer. Those glimpses of the mathematical workings of the world had always been more compelling to Charlie than whatever mundane input his eyes had to offer.

And then something hit him, and hit him again. It felt like being hit with a sledgehammer (or what he imagined being hit with a sledgehammer might feel like), and Charlie was suddenly paying attention again. The figure at the top of the room was still standing there, head up, face covered with a mask. As he watched, whoever it was turned, and ran. Charlie didn't process the image of the hand holding the gun until it was already gone.

He stumbled, and fell. His chest burned- it shouldn't burn, should it? And there was blood. This disturbed him, though he wasn't sure why. It couldn't possibly be his blood. Charlie reached for his phone.

Don sighed, and laid the papers on his desk. It was a quiet day- the first quiet day in some time, in fact. Quiet days were good, but they meant catching up on paperwork, which was just about Don's least favorite part of his job. He looked across the office at his team.

Megan was- no surprise- sitting at her desk, working at her computer. Colby, his arm in a sling after getting his shoulder stabbed, was leaning against David's desk, smiling as David said something to him.

Don rubbed his face with his hands, and leaned back. The last one had been particularly ugly. Kidnapping cases were always bad, and this one had been no exception. It was a federal judge and her daughter, and it had taken most of a week to find them, even with Charlie's math magic leading the way. Colby and the judge had both been injured in the course of the rescue, and Don himself had ended up shooting the perpetrator. As a death in the field always did, it had meant no end of paperwork and review.

Don's cell phone rang. He put it to his ear without looking at it. "Don Eppes," he said, brusquely.

On the other end of the line, he heard a woman crying, and someone gasping, "oh, my god, oh my god, oh my god…" Don tensed, unsure what to expect. Then he heard his brother's voice over the top of it.

"Donnie?" Charlie said, his voice shaky.

"Charlie?" Don said, concerned. "What's going on there?"

"Grey… ah- hoodie. And a mask. Sorry I don't know more, Donnie… Wasn't paying attention. So sorry." Charlie coughed, and Don could hear something liquid in it.

"What are you talking about, buddy? Are you okay?" Don stood up, headed for the door to his office.

"Hurts. Help me, Don? It- it hurts a lot…" Charlie's voice faded to nothing at the end.

"Charlie? What hurts?" There was no answer. Don clutched the phone, his heart racing. "Charlie?" There was panic in his voice. Others in the office turned to look at him, concerned.

"Doctor Eppes?" a girl said, in the distance. "Oh, my god, there's so much blood."

"He's not breathing," a male voice put in. "I'm going to-"

Don pulled the phone away from his ear, unable to continue listening."Megan!" he said, tamping down his fear. "Is there any report from the police of something happening at CalSci?"

"CalSci?" she said, concerned. "Is there something going on with Charlie, Don?"

"I-" He bit down on I don't know, and I think so, and alsoI'm afraid. Don's face was as blank as he could make it. "Just check."

"David will check, and get us the info while we're en route," Megan said, nodding towards the door. She pursed her lips. "You can tell me what's going on while we drive."

Don nodded, his mouth set in a tight, thin line, and headed for the door.