Mysterious corridors in space lead to the discovery of an ancient civilization.
Simone and Sipowicz investigate a young woman's murder, in which her former stepfather is a suspect; Lesniak investigates a con artist.
A little girl's imaginary friend becomes a frightening reality for the crew when she threatens to destroy the Enterprise.
Sipowicz's reaction to Lt. Fancy's departure is unusual; Russell and McDowell attempt to track down a dismembered body part for reattachment.