Six men have failed to appear in a West End court, so it's time for Scotland Yard to make a few undercover enquiries. They enlist the help of Detective-Constable Cordari, who leads them to a mysterious organisation smuggling criminals out of the country.

There ensues a relentless chase that moves to Algeria and back to London. In the meantime, Cordari has vanished in the same horribly mysterious way as others before him.