A boat collision ruins Lupin and Fujiko's quiet boating expedition. They discover a woman named Linda in the other boat just as gunmen on a larger boat attack them. After avoiding the gunboat, they learn that Linda is the assistant to a world-renowned expert on nuclear fission. She lived on an island with the doctor, which also housed the "Kirein Killers" ("Killers of the Sea"). Lupin and Jigen try to storm the island to save the Doctor and discover Linda's mysterious secret.