The tranquil planet of Aritani has suddenly come under attack by a vicious and unknown enemy. The Enterprise rallies to the scene, only to plunge into a deadly nightmare: Spock is found mysteriously injured, his mental powers crippled and weak, and Kirk uncovers an evil Romulan plot—with a cunning double agent in the middle. As Spock begins to regain his memory, Kirk strives to expose the agent. But only Spock's knowledge can stop the Romulans… from controlling the universe!