An American jazz pianist, blinded in a London bank robbery ten years before, makes his first return appearance in England at an engangement party where he believes he hears the voice of the gunman who cost him his sight.
The film is based on the actual events of the Portland Spy Ring trial in the U.K. A disgruntled Navy Clerk is transferred to a secret research establishment and is subsequently black-mailed/paid by Czech intelligence to procure secrets for them. He seduces the secretary who controls the most secret documents, and they enjoy the fruits of their treachery until the British authorities begin to close in on them.
The cat and mouse game between government agents and a spy ring that has taken secret documents from a plane crash in Germany, not far from an US military research centre.
An international criminal arrives in London, and a detective is anxious to pin something on him for some unprovable murders of former lovers. The villain starts to suspect servants and henchmen of being a police spy known as "Number Six".
Two rival gangs are trying to fix horse races and a jockey is attacked and left for dead in a stage-managed car crash. An insurance investigator makes routine enquiries into the "accident" and one of the gang leaders feels threatened by this and takes counter measures.
