“Time’s Arrow” (Part 1)
Written by Joe Menosky and Michael Piller
Directed by Les Landau
Season 5, Episode 26
Production episode 40275-226
Original air date: June 15, 1992
Stardate: 45959.1
Captain’s Log: The Enterprise is in orbit of Earth for a rare trip home. An archaeological dig prompted by the installation of new seismic regulators under San Francisco has revealed evidence of extraterrestrial life in the 19th century—the rock in the cavern has been altered by triolic waves, which wouldn’t occur naturally on Earth in the 19th or 24th centuries.
But that’s not the really bizarre part, nor why the Enterprise specifically was summoned. Amidst the various artifacts—a pair of glasses, a Colt revolver, a pocket watch—is Data’s severed head.
[Your head is not an artifact!]