This is an excellent episode notwithstanding the core idea being a central story point recycled from episode 3, "The Architects of Fear." In that episode, Robert Culp instead of Robert Duval is a soldierly man transformed into an alien as part of a strategic deception. Curiously, the scientist who effects the transformation, in both episodes, is played by the same actor, Douglas Henderson.
There the similarities end as this episode, whose chief writer is the distinguished dramatist, Robert Towne, provides a narrative medium for the recycled idea that is wholly superior to the earlier script. While the first script amounts to a disturbing example of extreme cruelty in service of a preposterous idea, the latter script effectively indicts human fear and the impulse to violence in the face of the unknown.