A hard-nosed Chicago cop is sent to London to bring back an American mobster being held for extradition. Brannigan in his Irish-American way brings American law to the people of Scotland Yard but has to contend with a stuffy old London first.

When Count Contini attempts to destroy the world's economy by masterminding the theft of $1 billion in U.S. gold, ICE chief MacDonald summons secret agent Matt Helm to stop him.