Pretty Anne Fielding (Dulcie Gray) has her pick of men. There's her boyfriend, the sophisticated Victor (Eric Portman), and now there's Jack... He's the humble bus conductor who comes to her rescue after the bus stalls and delays her journey by an hour. She was on her way to meet Victor at the Hampstead Heath fairground and Jack gallantly escorts her there. Sparks fly between the pair as they share ice cream and enjoy the fair while keeping an eye out for Victor. When they finally reunite, Anne and Victor head for home at the same time a young woman is found dead on the Heath. She appears to be the latest victim of The Strangler', a notorious serial killer who has already struck five times before. With Jack seen storming away from the scene and Victor's handkerchief found near the body, the police seize both men to appear in the lineup of potential suspects. A crazed game of cat and mouse ensues and Anne soon finds herself in serious danger. The police are up against time in this race to draw the threads together - but in the end, which neck will they close around? Will the police get their killer before he gets Anne?