The USS "Enterprise", under the command of Captain Kirk, arrives at the planet Beta III in the C-111 system where the USS "Archon" was reported lost nearly 100 years earlier. Lt. Sulu is the only member of the landing party who beams up from the planet's surface, and exhibits inexplicable euphoria. Kirk beams down with another party to investigate. They find the inhabitants living in a 19th-century Earth-style culture, ruled over by cloaked and cowled "Lawgivers" and a reclusive dictator, Landru. Their arrival is shortly followed by the "Festival", a period of violence, destruction, and sexual aggression.