An up and coming politician is caught in a compromising photograph taken by a maid, who turns out to be part of a sophisticated blackmail ring. When the girl is found murdered, he holds an incriminating old dueling pistol.

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".

The police investigate the murder of an officer, killed during a jewel robbery.

In Copenhagen, a former resistance fighter seeks the traitor responsible for betraying his comrades during World War II.

After the mysterious crash of a millionaire's private plane, scientists secretly harvest the dying man's brain and keep it alive in a laboratory in order to communicate via telepathy.