While giving his testimony in a retrial, Grissom sees fingerprints on a matchbox that he does not recall. The victim Max Larson was found dead I his hardware store hit by a wrench. He requests a recess to the DA and reopens the investigation of the case. He follows the protocol and assigns Catherine, Warrick and Nick to investigate the case again and why they have missed the fingerprint in their investigation. Ecklie asks Sofia to investigate Grissom's cases and begins a witch hunt in the laboratory. Meanwhile, Sara, Greg and Det. Louis Vartann investigate the case of a John Doe, who died after shooting his own leg. When they succeed to find the register of the gun, they find clue of another case.

CSI investigates the death of a toddler who was left in a cardboard box in a parking lot. A registered sex offender who is wrongly accused threatens Catherine after the real cause of death is identified.