The Road to Hong Kong

Diane recounts the events in a flashback to American Intelligence. She reveals that transmissions from missiles bound for the moon are actually American in origin, not Soviet. This framing sets up the rest of the story as a Cold War spy caper.

Harry Turner and Chester Babcock run a Do-it-yourself interplanetary flight kit scam in Calcutta that swindles gullible buyers. The scheme ends with Chester being injured, leaving him with amnesia. An Indian doctor insists the only cure lies with the monks at a Tibetan lamasery.

At the airport, Chester accidentally grabs a suitcase marked as the contact for The Third Echelon. Diane, a Third Echelon agent, is supposed to deliver Russian rocket fuel plans to that contact but mistakes Chester for the intended recipient.

In Tibet, they reach the lamasery and Chester's memory begins to recover under the monks' treatment. A Tibetan tea leaf recollects memories, and one giggling lama memorizes Lady Chatterley's Lover. Meanwhile Harry plots to steal a bottle that would grant Chester an even stronger photographic memory for nefarious purposes.

Back in Calcutta, Diane follows with Chester. Chester memorizes the rocket formula that Diane has planted in his coat as proof of the herb's effect. Unaware of its nature, Harry destroys the formula after the memorization. Diane arrives too late but offers them $25,000 to meet her in Hong Kong.

On the way to Hong Kong, an agent of the High Lama replaces the stolen Tibetan herb bottles with ordinary tea leaves. The substitution foils any attempt to reuse the memory-enhancing substance.

The Third Echelon wants the fuel for an underwater launch pad in Hong Kong to be the first on the Moon. Their goal is to launch nuclear weapons and control survivors on Earth.

To gain international prestige, they switch from apes to sending Chester and Harry as human astronauts for the Moon mission. The launch succeeds and returns with Chester's memory enhanced by the experience. During the flight they are treated as guinea pigs and even fed bananas.

Diane defects from the Third Echelon when she finds out they plan to dissect Chester and Harry. She helps the two escape, and they are chased through Hong Kong.

The pursuit continues through Hong Kong as Diane guides the authorities toward stopping the Third Echelon. Chester and Harry encounter Dorothy Lamour at a nightclub, where they are recaptured by the organization.

Chester, Harry, and Diane end up aboard a rocket bound for another planet. They think they are alone after landing, but they are not – Chester shouts 'The Italians!' as Frank Sinatra and Dean Martin join them.