Unknown to everyone but his shady Middle Eastern bosses, watchmaker Hawkins is actually a professional hired assassin with a predilection for killing his targets with bombs. After disposing of a dictator and millionaire, Hawkins is assigned to kill a politician who is heading to a remote hotel, The Green Man, for a secret tryst with his secretary. There, however, Hawkins' plot is discovered by vacuum salesman William Blake, who determines to stop him.

Alastair Sim
as Hawkins

George Cole
as William Blake

Terry-Thomas
as Charles Boughtflower

Jill Adams
as Ann Vincent

Raymond Huntley
as Sir Gregory Upshott

Colin Gordon
as Reginald Willoughby-Cruft

Avril Angers
as Marigold

John Chandos
as McKechnie

Eileen Moore
as Joan Wood

Arthur Brough
as Landlord