Forced to disguise themselves as interstellar traders, Captain Kirk and Mr Spock ae trapped on the primitive world of Organia as Klingon Defence Forces occupy the planet. The Organian people are their best hope that the Federation can stop the Klingons -- and yet they are avowed pacifists. When Kirk and Spock sabotage the Klingons in an attempt to show the Organians that they can fight back against Klingon oppression, the Klingon commander, Captain Kor, retaliates by executing Organians in reprisal.

Unmoved, the Council of Elders pleads with Kirk and Spock to stop the violence. Meanwhile, out in deep space, Starfleet and Klingon forces scramble to position their fleets for the first onslaught of what could be a long and deadly war.