Agent Joaquín recalls his latest mission while lying wounded in an ambulance: Joaquín has infiltrated a band of smugglers. When the villains learn the truth about him, they kidnap Joaquín's fiancee. Santo comes to her rescue and fights the band. Filmed at the same time as Santo vs. the Evil Brain, Santo vs. the Infernal Men was also shot in Cuba, and ended just the day before Fidel Castro entered Havana and declared the victory of the revolution.