This newly restored Cuban-Mexican horror-action cult classic opens with three gangsters cornering Santo in a deserted alley and knocking him out. He is then taken to the laboratory of a crazed Doctor Campos and turned into a docile servant through a series of injections and electric shocks. Filming ended just the day before Fidel Castro entered Havana declaring the victory of the revolution, forcing the filmmakers to flee prematurely with the unprocessed 35mm negative smuggled inside a coffin.