When the body of Vanessa Keaton is found drowned in water fountain in a gated community and hit on the forehead, Grissom, Sara, Greg and Capt. Brass assume the investigation. Soon they learn that Vanessa was in a swingers' party, but the water in her lung is not from the fountain. They interview the owners of the house and guests and collect the water in the swimming pools to see if any of them match the water in the lungs of Vanessa. Mia examines the DNAs in the several condoms in the garbage bin. Meanwhile, Warrick, Nick and Det. Chris Cavaliere investigate the murder Mr. Basengi, the landlord of a video arcade. They find an eviction notice to the tenants are Melissa Poolie and Charlie Pinscher that become prime suspects. They visit Charlie that tells that Melissa was his girlfriend and left him with the rent. They learn from Marty Gleason, a member of the crime scene cleanup, that the place has a decomposed smell and Warrick and Nick find the body of Melissa hidden in a game and Charlie is brought back to the interrogation room.

After a cop convicted of killing his police officer wife is killed in prison, the team discovers that he may have been framed, and Brass and Vartann may have been romantically linked to his wife.