UNCLE sends Solo and Petros, another agent, to Irbos, an island near Greece. They discover that Dr. Killman, a Thrush scientist, has enslaved the island's population to build a new destructive device. Filene, a Thrush official who has just arrived on the island, is accidentally killed during a fight. Solo takes his place, the basis of the episode title. Meanwhile, Petros is captured. Thrush is impatient and is ready to end Dr. Killman's project, complicating Solo's situation.