Boom
S1 episode 13 Aired on February 8, 2001

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.