Shadow of Fear(1963)

Overview:

An American returning home from Baghdad and seeing his girl in Britain on the way agrees to take a message to the secret service. Once in London he is picked up by the gang involved, who have by then killed the original Middle East agent. He escapes, but he and his girl friend are a marked couple as they retreat to Seaford on the south coast to act as bait in an MI5 plan to catch the thugs.