Catherine takes the point in the investigation of an escalating series of peeping tom incidents. The crew is racing to stop the attacker before his crimes become more serious assaults. Meanwhile, Sara reopens the dormant case of her friend, a district attorney. The DA is facing surgery to remove a bullet she got in an attack that killed her husband three years prior.

A bowling tournament is disrupted when an important piece of evidence is uncovered, leading the CSIs to investigate a murder at the same bowling alley.