A team comprised of various intergalactic experts, amongst them are Kirk and Spock, must recover an artifact known as the Soul of the Skorr. The theft must be kept secret, or a galactic holy war could break out.
The Enterprise is transporting its first Captain, Robert April to Babel, where he will reluctantly accept his retirement. When the Enterprise attempt to stop an unidentified vessel on a collision course with the Beta Niobe nova, the ship accidentally pass into an alternate dimension, where time flows in the opposite direction. The crew of the Enterprise rapidly begins to grow younger in age, and soon become unable to man the consoles.