Boom (S01E13)

A deadly bomb explosion at a Vegas office building sends Grissom and the CSI team in search of a serial bomber, and their primary suspect is the building's overly helpful security guard who knows more than he should about blowing things up. Meanwhile, Nick's one-night stand with a call girl he's helped in the past puts his DNA and fingerprints at the scene of her murder, and it's up to Catherine to try to prove his innocence. (USA Network)