This season-ending cliffhanger finds the Enterprise called back to Earth because of artifacts discovered in a cavern. Most of the artifacts are from 19th century Earth except for one - the remains of Data's head apparently left there sometime in the past where Data was destroyed. The crew finds traces of Triallic Waves in the cavern and traces them back to Devidia Two where they find yet another cave - this one inhabited by beings who are slightly out of phase with our universe. Data assists Geordi in building a Sub-Space distorter to align the synchronic distortion. As Data uses the distorter, the beings inhabiting the area use a temporal distorter and Data is caught in the waves and sent to Earth in the late 19th century.

Producer: David Livingston
Teleplay: Joe Menosky, Michael Piller
Story: Joe Menosky
Director: Les Landau

Guest Cast:

Jerry Hardin (Samuel Clemens)
Michael Aron (Bellboy)
Barry Kivel (Doorman)
Ken Thorley (Seaman)
Sheldon Peters Wolfchild (Indian)
Jack Murdock (Beggar)
Marc Alaimo (Gambler)
Milt Tarver (Scientist)
Michael Hungerford (Roughneck)