A routine survey of the planet Alpha Octavius Four turns disastrous when Spock is attacked and poisoned by a huge creature and Kirk's landing party is trapped underground by a violent earthquake. As Spock fights for his life in sickbay, Scotty organizes a search for Kirk and his men. However, rescue effort cease when the U.S.S. Enterprise is called away to the Beta Cabrini system where a mining colony is under heavy attack.
At Beta Cabrini, the Enterprise faces off against a Marauder named Dreen, a man that Spock had watched his former captain Christopher Pike defeat years before. Fighting the effects of the poison, Spock struggles to his feet and takes command of the ship. Soon, Spock and Dreen are locked into a deadly game of cat and mouse, a game driven by mad revenge that can have only one survivor.