Solo and Illya investigate a series of kidnappings that lead to a modern-day pirate ship run by Captain Shark (Robert Culp), who is filling his Noah's Ark with craftsmen from all walks of life to repopulate the world after the nuclear holocaust he feels is imminent. With the help of Harry Barnman (Herbert Anderson) and his wife Elsa (Sue Anne Langdon). Solo and Illya pose as shipwrecked sailors to in turn wreck his plans.

Solo gets an unwelcome young companion (Kurt Russell), a ten year old who wants Solo to marry his widowed mother, in his efforts to find the source of a deadly chemical that killed an entire Scottish village. In a race to find the source with General Yokura (Leonard Strong), Solo eventually uses a ring on the finger of a statue to pinpoint a cave where the deadly chemical has leaked from, but has to use his wits to escape when he is trapped there by Yokura and his men.

Solo and Illya agree to help Major Morgan (Gene Raymond), Solo's old commanding officer, steal a national symbol sceptre for his people from a dictator. Morgan is killed and Solo and Illya and Zia (Ziva Rodann), Morgan's female aide, are captured and sentenced to death. After they escape, they find that Morgan is still alive and has duped them into stealing the sceptre for him because of the precious gems it contains.

Solo attends a revival meeting conducted by evangelist Brother Love (Eddie Albert), who is actually a THRUSH leader constructing a nuclear spaceship with the aid of a kidnapped scientist, Dr. Hradny (Robert H. Harris). College student Pearl Rolfe (Maggie Pierce) is kidnapped by Love's followers, and Solo must rescue both victims and destroy Love's plan at the same time.