Anan-7
David Opatoshu

Sar-6
Robert Sampson

Mea-3
Barbara Babcock

Ambassador Robert Fox
Gene Lyons

Yeoman Tamura
Miko Mayama

Lt. Galloway
David L. Ross

Lt. DePaul
Sean Kenney

Citizen of Eminiar VII
Eddie Paskey

Despite warnings from planet Eminiar VII in the star cluster NGC321 to keep away, the Enterprise - at the insistence of its passenger Ambassador Fox - arrives to open diplomatic relations. Kirk and a landing party beam down and are met by a girl called Mea3 who escorts them to Anan7, the leader of their High Council.

They are informed that the planet has been at war for 500 years with its neighbour, Vendikar, although they can see no signs of conflict. An alert sounds and doors open in the chamber revealing a high-tech computer controlled war room which is registering attacks and apparently launching missiles in retaliation.

The Enterprise advises that it is not detecting any activity and the mystery is solved when Anan7 explains that the entire war is theoretical and has been conducted for years by the computers in order to avoid the real horrors of battle. All casualties are calculated by the computers, following which Kirk is advised that the Enterprise has technically been destroyed. He and the crew have 24 hours to report to a disintegration station.

The landing party is imprisoned and Anan7 makes an unsuccessful attempt to persuade Scotty and the rest of the crew to beam down, which alerts them to the situation. In the meantime, Kirk and his party escape and destroy a disintegration chamber. Anan7 launches an attack on the Enterprise but her shields are already up and Scotty refuses to lower them despite Fox's orders to do so.

Kirk manages to get to Anan7 but is arrested, as are Fox and his assistant when they beam down to the surface. Spock effects a rescue after which they go about systematically destroying the chambers. Scotty receives orders from Kirk to destroy the planet in two hours unless advised otherwise.

Kirk and the others then proceed to start disabling the war computers leaving Anan7 and his opposite number on Vendikar with the choice of either starting a full scale real war or begin talking to each other to work out a peace settlement. Vendikar is as afraid of real war as Eminiar VII and agrees to negotiate, with Ambassador Fox staying behind to assist with the arrangements after the departure of the Enterprise.