He didn't stand on top of the roof but sat on the edge of it, looking below at the world where his legs dangled freely. An airplane flew overhead but he couldn't hear it, the noise of the world being muted by the pounding of Marilyn Manson in his headphones. He let his torso drop backwards and rested his head on the roof of CSI under him. The sky was blue, so very deeply blue that it almost hurt his eyes. He closed them and let the world disappear so that all that was left in existence besides his thoughts was the screaming, pounding music. He let the music carry him away.
In a few minutes, he would have to go back inside the building and wear his goofy smile again and be happy-go-lucky again, just like always. After all, he was just the geeky lab rat who listened to his music too loud and had too much energy for his own good. That was who he was. If he had real thoughts, real feelings, and went to work without playing around with a piece of evidence or cracking a sex joke with Catherine whenever he could, then what the hell was wrong with him? He's just always happy.
To be fair, the happiness that he had often exerted at work hadn't always been faked. He liked going to work, or at least he used to. He liked the people he worked with. He liked being the goofball with weird hair. Even still today, he was a pretty geniunely happy person. His life wasn't full of angst and drama and dead girlfriends and screaming parents or anything like that. There were a lot of good things in his life. But this wasn't some stupid movie or T.V. show. He was a real person. And real people have got bad in their lives as well as good, and sometimes he felt that his co-workers didn't really see him as a real person. Sometimes, he wondered if they even saw him at all.
Mostly, he didn't have problems with his co-workers. He had used to have this big crush on Sara but he knew that was never going to happen in a million years: the closest thing Sara could see him as besides a geeky lab rat would be a pesky little brother. But that was okay because he liked Sara and he enjoyed bantering back and forth with her. He had the same bantering relationship with Catherine and Warrick, and that was fun too. Of all the CSI's, he probably felt closest to Nick, and that could have been because Nick was more personable or younger or whatever. He knew, though, that if he was in some sort of bind or an emergency, and he needed to call someone from work, his first thought would be to Nick. If Sara was his annoying, over-mature older sister, than Nick was definitely the big brother, and that was cool. He valued Nick's friendship more than any other relationship he had at CSI.
But Grissom. . .
No one really knew what to do with Gris. Everyone had their own problems with him. Catherine wanted him to be a more open friend. Nick wanted Grissom to trust his judgement as a CSI level 3. There was something going on between Sara and Griss, though God knew what, and Warrick mostly just didn't want to disappoint Grissom. But whatever they thought or the relationship was, he knew that Grissom at least respected all of them as good, hard-working CSI's. And what did Grissom think of him?
Not a whole hell of a lot, as far as he could tell. He didn't know why it was so important to him to have Grissom like him, but it was. Grissom just seemed to have that affect on people. They liked him, respected him, worked for him, and didn't understand what the hell he was about. He was a mystery, their boss. And for some unexplicable reason or another, it was important that the boss thought well of him.
So it was of course Grissom that discovered his hands were shaking after the explosion in the lab. Not Nick, who would have understood and watched out for him, and not Sara, who would have probably been to engrossed in work to really care, but Grissom, his boss. Even lying on his back on the roof, Greg shook his head to himself. He still didn't know what Gris had thought. Did he care? Was he only worried about work? Should he be worried?
He didn't know. Work had used to be fun for him but now it took all his energy to smile like the big goofball everyone knew him as and go back to work. He worried at every test he ran that he would turn around and his lab would blow up. But this time would be worse because this time he wouldn't get let off with severe burn scarring to his back. This time he'd be dead and everyone would get to stand above him in the autopsy room, cutting open his corpse to confirm it was explosion that killed him.
He shook his head again and turned the music even louder. "But I'm not a slave to a God that doesn't exist," Marilyn Manson pounded through his headphones. "But I'm not a slave to a world that doesn't give a shit."

Did the world give a shit? Usually, he wasn't a big believer in the music he listened to; he just liked the beat, rather than believed the words. But lately, he wondered, did the world give a shit? Did God? Did He even exist?
He opened his eyes. The sky was so very blue. It reminded him of another Marilyn Manson lyric. "Dear God, the sky is as blue as a gunshot wound. Dear God, if you were alive, yeah, you know we'd kill you."
Break was almost over. Soon time to go back inside. Back to work.
He hated work now. He never considered himself to be a brave soul, but work now filled him with such a fear that he loathed himself for being such a chickenshit. He hated that work scared him so much and he hated that he was such an idiot and he hated that Grissom didn't see him as a real person and he hated that God didn't exist. He hated that if he knew God was alive, that society would kill him. He wondered if he could kill God for all the shit he's done, would he?
He didn't know.
He sat up again and went back to watching his legs dangle off of the roof freely. He didn't want to go back inside. Inside, he was just another geek whose hands shook as soon as he touched a test tube or a hot plate. He looked down at his hands now. They were steady.
Outside, he was safe from the explosion. Outside, he was free from having to put on his happy mask.
If God was alive, he wondered what kind of mask He wore.
People walked around below him. They had no idea. They didn't see him. They didn't see.
No one saw.
Outside he was alone but free. Inside, he was surrounded by other people-yet somehow, he was still alone anyways. Inside, he was trapped. He didn't want to go back again. He was terrified of going back inside the box.
The people below didn't see his terror. They continued with their daily business. He stared at them from his sitting position on the roof top and wanted to cry.
He didn't, and went back inside.