Some time has passed since Part 1, as Picard and the away team members, passing themselves off as a theatre troupe, are behind in their rent at a boarding house in 19thC San Francisco. (We already know [s5e16 “Ethics“] that LaFoge’s visor lets him see through at least some playing cards, and Troi’s access to emotions and sometimes specific thoughts would presumably help her tell when players are bluffing, so presumably they could acquire plenty of money — but this script doesn’t go there.)
Looking smashing in period costumes (Picard is a lamp lighter, Riker a cop, Crusher a nurse) they track the aliens who have, under the cover of a fake cholera epidemic, been sucking the life energy out of citizens.
While Data easily convinces Guinan that he’s from the future, in a plot twist I didn’t remember, the suspicious Mark Twain believes he’s protecting the human race from an alien invasion, and ends up hampering Data’s efforts.
An encounter with a young Jack London, Data driving a team of horses to rescue his crewmates, and a some surprise visits from Mark Twain help advance the plot, but the last act drags back on the Enterprise-D as Twain monologues cantankerously while Troi walks him through the ship, and back in 19thC San Francisco as Picard stays behind to tend to an apparently injured Guinan.
While the glowing time-shifting aliens were appropriately creepy, their strategy of carrying around an ostentatious snake-headed walking stick, and using the same disguises in the same location wasn’t really all that bright. In addition, because none of the characters we got to know in San Francisco were personally threatened by the aliens (who seemed to be low-key pursuing victims who were already near death), the suspense/horror angle was downplayed. The Twain character and the Picard/Guinan relationships needed attention, so as the action builds the aliens don’t get much time to speak for themselves. That makes them into monsters defeated with photon torpedoes, rather than sentient beings we can understand and perhaps learn to trust.
I remember being disappointed by the revelation of what Guinan meant many episodes ago when she cryptically said her closeness with Picard went beyond friendship and beyond family; and I remember thinking we were spending too much time with Twain.
A final bit of cleverness by Picard and a practical suggestion from Twain helps to close the time-travel loop. Not a great episode, but because TNG was famous for its humanistic optimism, it was refreshing to see the cynical and bitter Twain get excited by Trek’s vision of a tolerant, peaceful, plentiful future for all.
At the same time, it was also kind of depressing to be reminded of how much work society will have to do in order to combat the ignorance, conspiracy theories, tribal cultism, racism, glorification of violence and economic disparity that works against the bright future TNG imagined.