World War II vet Frank Pryor (Lloyd Bridges) returns to London from America after six years to look up an old flame, Pauline French (Moira Lister), now a successful actress. As he and the other passengers leave the plane and walk across to the terminal, Frank pauses for a moment and asks the man beside him for a light. There’s a gunshot and the man crumples to the ground, shot by a marksman with a high-powered rifle, an assassin with a limp. It’s not long before Frank Pryor is up to his neck in murderous intrigue.