Murder's a swine

When newlyweds Agnes and Andrew Kinghof are present for the discovery of an over-ripe corpse in the air-raid shelter of their apartment building, the two set out to put their amateur detective skills to work (much to the chagrin of Andrew's uncle at Scotland Yard). The dead man's sister, a neighbor, is nearly frightened to death by the appearance of a grinning pig's head outside her window, and she claims to be threatened by someone calling himself 'The Pig'. The newlyweds deduce that it must be someone who lives in the same apartment building, which houses, amongst others; a medical student, a civil servant with fascist sympathies, and a French widow.