Harry Hawkins is a freelance assassin who is contracted to blow up Sir Gregory Upshott, a prominent and pompous London businessman.

By courting Upshott's spinster secretary, Marigold, he learns that his target will be taking one of the firm's typists for a weekend at a seaside hotel called "The Green Man".

Finding out his treachery, the secretary comes to his house to confront him but is attacked (unseen by the viewer) and left for dead by Hawkins' assistant McKechnie who, as nobody is next door, hides the body there (in a grand piano).

William and Ann then face another moment of horror as the "corpse" staggers into the house through the French doors and, before collapsing again, tells them that Upshott will be blown up that night in the Green Man by a bomb at precisely 22:28.

[5] The Monthly Film Bulletin wrote: "The opening scenes (Hawkins describing his past triumphs as an assassin and the attempted murder of Marigold) strike a lightly macabre note and suggest another essay in "black" comedy.

Alastair Sim extracts the maximum amount of ghoulish humour from a sketchily written part, TerryThomas is intermittently amusing in his now familiar act and the direction is brisk.

"[7] The Radio Times wrote "If you ever doubted that Alastair Sim was the finest British screen comedian of the sound era, then here's the proof of his immense talent.

As the assassin with the mournful smile, he gives a performance of rare genius that more than makes amends for the longueurs in Frank Launder and Sidney Gilliat's script.

"[8] Allmovie opined "If The Green Man finally falls a little short of being classic, it's only because the mechanics of the plot get a bit wearying at times; otherwise, it's a charmingly subversive little treat.