An archaeologist who’s not very good at prioritizing natters on to Picard about finding some old glasses, a revolver, and a pocket watch in an old mine. When Picard asks why the Enterprise-D was recalled to Earth to investigate, only then does the archeologist say oh yeah, here in this old mine that’s been sealed under San Francisco for 500 years we also found the severed head of Data. (Cue the opening credits.)
This Data-focused story gives us some touching moments as LaForge, Troi, and Riker adjust to the foreknowledge that their colleague will at some point be decapitated. I actually went “awww!” out loud when Riker quoted Data’s obtuse droid-splaination of friendship, and Data replied, “I am also fond of you, Commander.”
But this is episodic TV, so before the next commercial break the Enterprise encounters a timey-wimey PCF (plot contrivance field), and Data soon finds himself in 19thC San Francisco.
Some fish-out-of-water comedy, a poker game, a chance encounter with Guinan from 500 years ago, and an inconveniently eavesdropping Mark Twain pass the time pleasantly enough. On the street, we watch a grim-faced gentleman with a snake-headed staff and a woman carrying a bag, as they harvest a glowing soul-ball that emanates from an old beggar at the moment of his death.
Back on the planet where the Enterprise-D is investigating, we see two aliens with this same snake-staff and bag, supplying a storage unit with glowing soul-balls for other aliens to ingest. And, as if sensing that it’s time for the “To Be Continued…” overlay, Picard signals the away team to follow those aliens through their glowy time rift.