Pretty young heiress Phyllis Leighton is kidnapped while on vacation in Bangkok. The authorities are baffled. The girl's wealthy mother asks world-famous private detective Joe Walker (a.k.a. "Kommissar X") to investigate. Once in Bangkok, Walker is attacked by assassins with poison gas and flamethrowers. Each assailant bears a tattoo of three golden serpents entwined on his wrist. They lead the private eye to a remote island where Leighton and other girls are being sold as slaves to the highest bidder. Walker vows to save their virginal bodies from a fate worse than death...but to do so, he must take on the deranged serpent cult that holds them captive...
In the United States, advertising for Island of Lost Girls luridly boasted that it was based on real-life events. The film is actually a dubbed version of Three Golden Serpents, one of a series of seven pictures based on the Kommissar X crime novels from Germany. Starring model-turned-actor Tony Kendall as the womanizing private eye, all of them were very influenced by the-then prevalent James Bond craze. Island of Lost Girls was shot on location in Thailand and features more sex and violence than the prior Kommissar X films, a sign of the changing times.