Rosser, Cyril Cusack, a British agent, disappears in Beirut. MacGillivray John Le Mesurier, the British intelligence boss, has difficulty finding a trained agent on short notice, so he recruits Dr. Jason Love David Niven, a doctor who has done intelligence work before, to uncover what is going on. As a doctor, Love can attend a medical convention there without attracting suspicion.
Love stops off in Rome and meets his contact there, a fashion model named Vikki Françoise Dorléac. The two hit it off, and Love misses his flight to Beirut; he watches it depart, only to see the plane explode in mid-air as it crashes in a cataclysmic burst of flame.
Love arrives in Beirut and teams up with another agent, Parkington Nigel Davenport. Together they uncover a communist plot to assassinate the pro-British Prince of Zahlouf, a maneuver designed to threaten Britain’s eastern oil interests. The plan unravels when Parkington is killed by an enemy agent after revealing that Rosser is dead.
Back at his hotel, Love is stunned to find Vikki waiting, supposedly there on a photoshoot, but she confesses that she is a double agent and urges him to get out of Beirut as soon as possible.
Having learned of the assassination scheme, Love foils the hit by wrestling a rifle away from the man masquerading as one of the background “Arabs” in Vikki’s photoshoot. The rifle fires, striking someone in the crowd gathered to witness the Prince, and Love, still holding the weapon, is mistaken for the assassin by an enraged mob. He is driven onto a nearby roof, where a helicopter comes to his rescue—only to reveal that it is manned by the Russians, who have come for the real target, not to save him.
On board the jet Dove of Peace, Stanilaus [Ronald Radd], the top Russian spy in the region, smuggles Love aboard and attempts to extract information. Love speaks honestly, but Stanilaus does not initially believe him. Also on board is Vikki, returning to learn what her next assignment will be.
The defection of Simmias [Paul Stassino], the Russian agent responsible for the failed operation, shocks the British; he reveals Love’s predicament from the safe distance of the aircraft. As the jet travels over Canada, the British arrange a staged emergency to ferry victims out, but Stanilaus refuses to land until he is convinced of the threat. Love, however, manages to activate a concealed device in a cavity in his tooth that disrupts the jet’s avionics, forcing Stanilaus to concede and help.
On the ground, suspicion grows as there are no obvious victims to extract, and Stanilaus orders the jet to take off again. In the ensuing struggle, Vikki shoots Stanilaus, allowing Love to slip away, but she is killed in turn, payback for her double game.
The mission leaves Love both grateful for the narrow escape and wary of the costs of clandestine power in a volatile region.
