When Hamburg ship's mate Klaus Brandt catches a thief one night at the port, his downfall is pre-ordained. For the thief turns out to be a young, attractive woman and the otherwise upright sailor allows her to slip away. Jenny is the star of a local dive bar, with a side-line in smuggling.

Harry Piel plays Harry Peel who receives an urgent telephone call from a friend who has returned from South America recently. The call is being made from the circus "Beely" and our hero arrives there too late to prevent the murder of his friend. Now Harry must find his friend's killer and go on a strange mission involving a hidden document.