In the shuttlecraft Copernicus, Spock, Uhura, and Sulu are en-route to Starbase 25 to deliver a stasis box—a rare artifact of the Slaver culture—which stops time inside so any object can last forever. The now-extinct Slavers used these objects to carry weapons, valuables, and other scientific instruments and data. The boxes can detect each other and evidence shows that another device is located nearby. Spock begins to investigate. The shuttle lands on an ice planet where hostile Kzinti lie in ambush with an empty stasis box. The Kzinti once controlled the entire empire but now are bound to keeping peace. However, many Kzinti still take part in raiding Federation shipping and seek Slaver weapons to regain control of their empire.

The Kzinti take the shuttle crew hostage in an effort to take the box and its contents. The Kzinti leader obtains the weapon, but while tampering with it he enables the crew to escape. Spock steals back the weapon, but Uhura is recaptured. After Sulu creates an explosion with the weapon, it is recaptured by the Kzinti, who are killed when the device self-destructs.

Cast:

William Shatner as James T. Kirk
Leonard Nimoy as Spock
DeForest Kelley as Leonard H. McCoy
James Doohan as Montgomery Scott
Nichelle Nichols as Uhura
George Takei as Hikaru Sulu

Guest Cast:

James Doohan as Kzin telepath
James Doohan as Kzin flyer
Majel Barrett as Slaver weapon
James Doohan as Chuft Captain
James Doohan as Computer

Creative Staff:

Written By: Larry Niven
Director: Hal Sutherland