Greg doesn't laugh anymore.

He thinks Greg doesn't laugh anymore, he amends in his head. Just because he hasn't heard Greg laugh for three years doesn't mean Greg hasn't laughed in three years.

So really, it's just that Greg doesn't laugh around him anymore.

And Gil wonders why that is. Did he make a mistake when he allowed Greg to become a CSI? Was it death and violence and a lack of faith in the human race that took the happier Greg from him? Did something happen to Greg three years ago that caused him to stop viewing life with the same enthusiasm he once had?

The he remembers the smell of chemicals on burning skin in a charred lab and stops, counts backwards, thinks a little harder, and realizes it's been four years since he's heard Greg laugh and he suddenly doesn't wonder anymore.

It's odd, really, how much he wants to hear Greg laugh.