Original Air Date: February 3, 1978

After several weeks off the air during the winter break, Phase 2 returns with one of the season’s most intense and physical stories.

The Enterprise responds to a distress call from the Federation colony on Karsia Four, where communications have suddenly ceased following reports of violent unrest among the settlers.

When Captain Kirk leads an away team to the planet’s surface with Dr. McCoy and Xon, they discover the colony in chaos. Longtime neighbors have turned on one another, families are divided into armed factions, and the once-peaceful settlement has collapsed into brutal tribal violence.

Investigating the cause, McCoy and Xon discover that the colony had recently installed an experimental behavioral-conditioning system designed to suppress aggression and emotional conflict. Instead of calming the population, the malfunctioning device has stripped away the psychological barriers that normally restrain humanity’s darker impulses.

As fear and violence spread across the colony, members of the away team begin experiencing the same emotional distortions themselves.

With time running out, Kirk and Xon must shut down the failing system while McCoy struggles to treat the colonists caught in the outbreak — before the colony destroys itself completely.

Although the Enterprise succeeds in stopping the device, the damage to the colony’s social order may take years to repair, leaving the crew to confront the unsettling realization that civilization may rest on a far more fragile foundation than anyone wants to admit.