Stardate 5718.3: The Enterprise is carrying a new drug to the mental hospital on Elba II, where it is hoped that the last dangerously insane patients in the Federation can finally be treated. But when Kirk and Spock beam down, they do not realize that the facilities have been taken over by the inmates, led by Garth, a former Starfleet captain who has also become a shape-shifter. Before anyone on the Enterprise realizes what is transpiring on Elba II, Garth has activated a shield to prevent the landing party from escaping.
teleplay by Lee Erwin
story by Lee Erwin and Jerry Sohl
directed by Herb Wallerstein
music by Fred Steiner
Guest Cast: James Doohan (Mr. Scott), George Takei (Lt. Sulu), Nichelle Nichols (Lt. Uhura), Walter Koenig (Chekov), Steve Ihnat (Garth), Yvonne Craig (Marta), Richard Geary (Andorian), Gary Downey (Tellarite), Keye Luke (Cory)
LogBook entry by Earl Green