Federation Dr. Barron and his two anthropologist chums are hiding behind a holographic "duck blind" observing the Bronze Age Vulcanoids of planet Mintaka III.
When their power generator fails, they are injured and one falls out the window. A local man is zapped by the faulty equipment, too. Beverly's conscience would not allow the Mintakan to die, so after healing his injuries she attempts the ol' Pulaski brain-wipe and drops him back at home.
The Mintakan, Liko, relates the tale of his 'death' and 'resurrection' to his daughter, Oji. His blurry memories are similar enough to old superstitions of Mintakan gods that he begins to preach a worship of 'The Overseer Picard'. His peers are skeptical, having long ago abandoned their beliefs in such things as ghosts and astrology. They don't even worship Sybok, the Vulcan Jesus long thought to have died fighting God in the center of the galaxy.
Riker and Troi indulge in a little cosplay date, I mean vital undercover away mission. They fail to discredit Liko's tales in the face of the injured and clearly alien Dr. Palmer. They then attempt to make off with Palmer, but Troi is captured.
Somewhat panicked at the thought of angering The Picard, Liko proposes punishing Troi for Riker's angel-stealing sin.
Picard beams up the Mintakan leader Nuria and presents a reasoned discourse on his total lack of godhood, his people's path of invention building on invention after invention to what now seems like magic.
Nuria witnesses the sickbay death of anthropologist Warren and she is convinced humans are not all-powerful. Picard arrives in time to stop Liko putting an arrow through Troi. Grieving Liko asks for his dead wife back, then begs, and finally turns his arrow on 'The Overseer'. Picard lets him shoot to prove his point.
"Who Watches The Watchers?" makes apparent what some viewers preferred subtle: Picard and by extension the Federation are essentially heathens. Most 24th century humanity nods along when you say 'religious belief is backward, dangerous, and irrational'. The happy ending is that Nobody needs to worship Nobody Nohow. It may not be a message universally accepted by a primarily Christian audience. But back when McCoy joked about showing up somewhere and declaring himself the archangel Gabriel he raised an important point: Starfleet and the Federation could very easily DO that. And they don't. Using their power to take advantage of people is simply not jake. Another reason I want to go to there.