Police Detective Jim Brannigan (John Wayne) is sent from Chicago to London to extradite a wanted American criminal, Ben Larkin (John Vernon). However, Larkin is kidnapped before Brannigan can apprehend him, igniting a manhunt throughout the city. Jennifer (Judy Geeson), a British police officer, is appointed to help Brannigan, who is frequently bewildered by English customs. Brannigan's harsh policing techniques also lead to constant clashes with Cmdr. Swann (Richard Attenborough).