Brian Catalano

J.D. (Zach Braff) strikes up a romantic relationship with an attractive social worker (guest star Elizabeth Bogush, "Beverly Hills, 90210") but he soon learns that Elliot (Sarah Chalke) is not only jealous but thinks his new squeeze is bad news. Meanwhile, Turk (Donald Faison) discovers that Dr. Cox (John C. McGinley) also has romantic designs on Carla (Judy Reyes) while Carla encounters hard stares from her fellow nurses when she strikes up a car-pool friendship with the hated Dr. Kelso (Ken Jenkins).

Lightman and his ex-wife, Zoe, witness the execution of a murderer they prosecuted 17 years ago and face the possibility that they sent the wrong man to his death.

The killer from The Execution of Catherine Willows returns with deadly results.

Mac becomes particularly protective of the only witness in his murder investigation, a young boy found in shock at the exhibit, who after seeing the grizzly crime, confuses the events at the museum with a comic book he was reading at the time. The team works to discover if the motive was money, given the curator's wealth, or if the witness has something to do with it when the CSIs find he has ties to the victim. (TV-14)

When a religious cult operating in Canada unearths a spacecraft similar to the one Scully discovered in Africa, a plot is set in motion to kill baby William.