In 1907, struggling ham Shakespearian actor Foster Twelvetrees (Frankie Howerd) is invited to give a performance at the house of the sinister Henderson family by the head of the family, Stewart Henderson (Ray Milland)
Foster discovers he is, in fact, the rightful heir to the Henderson fortune as well as a million pounds of diamonds that are hidden somewhere in the manor.
The Henderson’s try to trick Foster into revealing where they are but to no avail, and soon the bodies start piling up as someone in the house will kill for the diamonds.
Reggie Henderson (Hugh Burden) takes an instant dislike to Foster and a series of mini standoffs eventuate – from a battle over the last egg at breakfast to Foster being called “swine” endlessly.
After quickly working out Foster is the key to finding the missing fortune in diamonds, veterinarian Ernest Henderson (Kenneth Griffith) and his wife Agnes (Ruth Dunning) try to bump him off with an injection of poison.
As you’d expect in a Frankie Howerd movie, the saucy jokes come thick and fast. But the film also expertly mixes comedy with terror.