Trefayne
David Hillary Hughes

Ayelborne
John Abbott

Claymare
Peter Brocco

Commander Kor
John Colicos

The Federation's fragile peace with the Klingons is breaking down and the Enterprise is sent to Organa, a planet of strategic importance, to prevent it from falling into Klingon hands. En route they find out that war has been declared after being attacked by, and destroying, a Klingon vessel. Kirk and Spock beam down to the planet leaving Sulu in command. They are met by Ayelborne, the chairman of the Council of Elders, who takes Kirk to speak to the council while Spock explores.

He reports back that the culture is similar to that of mediaeval Earth and that no progress seems to have been made for millennia. Kirk explains the situation to the Organian council and offers them Federation protection, which they politely refuse despite Kirk's offers of education and new technology. Klingon ships arrive in orbit and attack the Enterprise. Sulu, following his orders, leaves the area, stranding Kirk and Spock on the planet.

The Organians, strangely, seem to be aware of the Klingon presence and help disguise the Starfleet officers as traders. A Klingon force soon arrives in the Council chambers and their commander, Kor, declares himself to be the new military governor of the planet. Because the Organians are very placid and passive Kirk, pretending to be a local trader called Baroner, stands out like a sore thumb when he raises objections to them, and is arrested, even though they do not know his true identity. Kor speaks to him and makes him the contact man between himself and the Organians, sending him back to the Council with a list of rules and regulations.

The Organians show no interest in defending themselves so Kirk and Spock carry out their own mission, destroying a munitions and fuel dump. They try again to persuade the Council to accept their help and are again refused, but Kor is spying on the Council chamber, discovers their true identities and arrests them. They find escape to be impossible, but six hours later the Organian Elders just walk into their cell and tell them that they cannot allow the Klingons to harm them. They all walk out of the prison, Kirk and Spock showing puzzlement at the lack of guards.

In reprisal for their 'escape', Kor orders 200 Organians to be killed and threatens more if Kirk and Spock are not surrendered to him. Ayelborne maintains that nothing has changed but Kirk decides to take action. He retrieves their phasers from the Council and he and Spock leave the Council Chamber. That evening, Kirk and Spock attack the Klingon headquarters and fight their way through to Kor's office. Klingon guards race to follow them but, before they can open fire, all the weapons in the room suddenly become red-hot, forcing them to be discarded.

At the same moment all the orbiting ships find the same thing happening to their controls. Ayelborne and Trefayne appear in Kor's office and tell them all that they cannot allow violence and insist that they will stop the war, despite Kor's disbelief and ridicule. They return to their natural state, beings of pure energy with no physical bodies, who are far advanced from the Klingons and humans.

Apparently, nobody has been killed and the culture of the planet is just an illusion created for the convenience of visitors. Kirk, Spock and the Klingons listen in amazement as the Organians tell them that, if they do not agree to cease hostilities immediately, they will paralyse all their military capabilities throughout the galaxy. So saying, they disappear from sight leaving Kor bemoaning the fact that the war 'would have been glorious'.