In part one of "Bringers of Wonder," Commander John Koenig (Martin Landau) lost his mind and crashed the ship he was piloting. After his crew saved him, Dr. Helena Russell (Barbara Bain) hooked him up to an experimental machine meant to soothe his fevered brain. Meanwhile, it seemed that Moonbase Alpha had finally been found by a rescue team made up of volunteers from earth. But the rescuers that looked like long-lost friends, family and lovers to everyone else, looked to Koenig like mountainous glowing heaps of gore.
In part two, Koenig finally convinces Dr. Russell and the shape-shifting science officer Maya (Catherine Schell) that these supposed earth people are really hostile aliens. The trio discovers that the creatures live on energy and need a nuclear explosion on Moonbase Alpha to feed their starving bodies. The aliens hypnotize three crew members into thinking they are back on earth performing seemingly benign activities when what they're really doing is setting up the means for that nuclear explosion.
Part two features: Maya transforming into a one-eyed, two-horned, walking purple people tosser; the gore-creatures lugubriously chasing an impostor through the corridors; and a conclusion full of metaphysical posturing, including Koenig's line, "It's better to live as your own man than as a fool in someone else's dream." You tell 'em, Koenig.