The Enterprise crew must navigate an undeclared war with the Klingon Empire while a scientific experiment involving Mr. Spock goes disastrously wrong, creating a dangerous duplicate. The Organians, a potential diplomatic resource, have vanished, leaving Captain Kirk to deal with the immediate crisis of two identical Mr. Spocks. One must be eliminated, but the choice carries immense implications for the mission and the fate of the Enterprise.

This novel, part of the Star Trek universe, presents a classic science fiction dilemma that challenges the crew's problem-solving abilities. The narrative focuses on the immediate crisis of a duplicated Mr. Spock and the difficult decision of his fate, set against the backdrop of an interstellar war. The plot explores the ethical and practical implications of such a duplication, forcing Captain Kirk into a difficult choice. The story's resolution likely hinges on the crew's adherence to Starfleet principles and their ability to overcome a seemingly impossible situation.