A secret agent possesses a ring that makes him invisible for a short time, once every 10 hours. He is in pursuit of an evil criminal mastermind but, at the same time, must evade an enemy agent who also wants the ring.

• DDL Cinematografica
• Patrick O'Neal
• Ira von Fürstenberg
• Donald Pleasence
• Henry Silva
• Nicoletta Machiavelli
• Howard St. John
• Sorrell Booke
• Tiziano Cortini