A woman nervously paid for her groceries at the opening of the episode, and was later shot and killed in the parking lot. The CSIs began their investigation as a possible gang shooting, but one of the witnesses told the investigators that the dead woman had a little girl with her as well, turning the case into a 418/427 a homicide and a kidnapping.
Doc Robbins was beginning the examination of the victim when the woman's husband, FBI Agent Daniele Moore, burst in uncontrolled. He told Brass and the CSIs that his wife was killed by Rylan Gauss, a pedophile that had recently been released from prison and had a grudge against him. He was vehement that Gauss had also kidnapped his daughter, and his older son who was discovered missing not soon after.
Rylan Gauss was apprehended at a park, and was kept from being shot by Agent Moore by the CSIs. Brass interrogated Gauss as the CSIs searched his apartment for evidence. They discovered children's books and CD's, but Gauss' alibi checked out and no finger prints could be found to link him to a crime.
After looking over the evidence it appeared that Agent Moore had a motive to kill his wife. Agent Moore was found standing over Rylan Gauss' body, but neither of his service weapons were used in the shooting.
The prints found on a sandwich wrapper from the Moore's minivan came back as a match to Trent Moore, Agent Moore's son, and research of the spilled medication found in Trent's apartment were used to treat schizophrenia. A ball cap found in Gauss' apartment placed Trent at the scene. Agent Moore reluctantly told the police where his son might have gone to hide.
Trent was discovered in a shed where his parents' house used to be. The gun he was found with was a match to the bullets that killed Rylan Gauss, but not the bullets that killed his step-mother. Trent was off his medication and in the middle of a full psychotic episode and thought that he was Rylan Gauss. His father, Agent Moore, confessed that he had killed his wife in an attempt to bring Trent out of his episode and find his sister.
Bedbugs found in the baseball cap and images from traffic cameras helped the CSIs and the police locate Agent Moore's daughter, who was alive in a motel where her brother had taken her. Agent Moore was arrested, and Trent was in the hospital to receive treatment for his condition.