For me, this episode was just too vague. The idea is very good; Nick flashes back to three separate cases at the same motel, involving the same girl, who eventually becomes a murder suspect.
Given the fact that Nick was shown to be very emotionally involved in the story, I was waiting for some reason. For the first twenty minutes, all we got was a pretty much one-way conversation about science that didn't go anywhere. In the second case, she gives a random one-liner that is standard for teenagers ("My life is over!") and stalks away, with no more explanation. After that, she's dead.
So far, it seems to me that Nick's becoming a bit of a pedophile with the creepy looks, but that doesn't seem like a great plot.
Not to mention, the crime aspects of the episode weren't that great, either. The first case was introduced and solved in the blink of an eye, and had absolutely no relation to the rest of the episode. It's only use was to introduce the family, and a simple suicide might have done much better. The other cases, the one that matter, could have been given more consequence.
Frankly, all the emotions are baseless. The mother isn't psychotic enough, the girl isn't interesting enough, Nick isn't involved until the last three minutes, and Ray's concern was overdone. What happened to the wisecracks and character connections of CSI in its prime? Frankly, my two favorite moments were Greg talking to Nick at the first crime, and Riley mixing up her words with the horny couple. The rest of it was just... off.