'Time's Arrow' (Part II) (Story Code 227) by Jeri Taylor Story by Joe Menosky

When Lieutenant Commander Data's severed head was found in a sealed cavern on Earth, together with artefacts dating back to the Nineteenth Century, the crew of the U.S.S. Enterprise set off to unravel the mystery. However, after following the trail of time-travelling, shape-shifting aliens to the planet Devidia II, Data became trapped in Nineteenth Century San Francisco; here he met a younger version of Guinan, and the inquisitive novelist Samuel Clemens, a.k.a. Mark Twain, who soon decided to follow the two of them in the mistaken belief that they had travelled from the future to destroy the Earth... Captain Picard, Commander Riker, Lieutenant LaForge, Doctor Crusher and Counselor Troi follow their comrade through the time-rift, emerging in San Francisco some four hundred years earlier. Investigating a local morgue and infirmary, the away team discover that aliens from Devidia II have taken on the human form of a doctor and a nurse, and, using a device disguised as a cane, are stealing neural energy from cholera patients and then sending it back through the rift to feed their people. Encountering the aliens, Beverly snatches the cane; the creatures attack, but the Enterprise team are saved by the timely arrival of Data in a horse-drawn carriage. Back at Data's hotel room, the group conclude that that the cavern where Data's head was found acts as a focusing device to enable the aliens to travel through time; they return to the cave, unaware that they are being trailed by Clemens. But then the aliens burst in, retake the cane and activate the time-rift; a sonic boom resounds around the cavern, throwing Guinan against the wall and severing Data's head from his body, which promptly vanishes into the portal. While the alien nurse lies wounded, the doctor manages to escape through the rift, closely pursued by Riker, Geordi, Troi, Beverly - and Clemens. Picard is forced to remain behind with the injured Guinan - but then the portal closes, trapping the captain in the Nineteenth Century…

Patrick Stewart (Captain Jean-Luc Picard), Jonathan Frakes (Commander William Thomas Riker), LeVar Burton (Chief Engineer Lieutenant Commander Geordi La Forge), Michael Dorn (Security Chief Lieutenant Worf), Gates McFadden (Doctor Beverly Crusher), Marina Sirtis (Councelor Deanna Troi), Brent Spiner (Lieutenant Commander Data), Whoopi Goldberg (Guinan), Jerry Hardin (Samuel Clemens), Pamela Kosh (Mrs. Carmichael), William Boyett (Policeman), Michael Aron (Bellboy, Jack London), James Gleason (Doctor Appollinaire), Mary Stein (Alien Nurse), Alexander Enberg (Young Reporter), Bill Cho Lee (Male Patient), Majel Barrett (Computer Voice)

Directed by Les Landau
Produced by Peter Lauritson
Co-Produced by Ronald D. Moore
Co-Executive Producer Jeri Taylor
Executive Producers Michael Piller and Rick Berman

TX:
21st September, 1992

Notes:
*Featuring Captain Jean-Luc Picard, Commander William Thomas Riker, Chief Engineer Lieutenant Geordi La Forge, Security Chief Lieutenant Worf, Doctor Beverly Crusher, Councelor Deanna Troi, Lieutenant Commander Data and Guinan