When Vince Treadwell spots a famous jewel thief in Soho one night and the next day reads about a daring robbery at the Ritz, he takes it upon himself to investigate the case as the missing jewels belong to the beautiful French movie star Capuchine, with whom Vince is smitten. But it soon leads to murder - and he is the chief suspect. In prison and looking at a life sentence, Vince is offered a lifeline from his old friend at Interpol, Ray Dryden. He wants Vince to go undercover and return the jewels to the movie star, who is secretly dating hotshot producer, Carlo Messina. But in reality Messina is one of the biggest gangsters in Marseille , running a heroin pipeline to America. So after a daring prison escape, and armed with fake jewels, Vince finds himself on the French Riviera - and it just happens to be the eve of the 1965 Cannes film festival. Against the backdrop of movie star glamour, Vince soon finds himself embroiled in a deadly game of cat and mouse with the charismatic and psychotic criminal; a man for whom movies and reality are indivisible, and murder and mayhem are on the script.