Synopsis:
On a late afternoon, two brilliant young
aesthetes, Brandon Shaw and Phillip Morgan ), murder a former classmate, David Kentley, in their apartment. They commit the crime as an intellectual exercise: they want to prove their superiority by committing the "perfect murder".
After hiding the body in a large antique wooden chest, Brandon and Phillip host a dinner party at the apartment which has a panoramic view of Manhattan's skyline. The guests, unaware of what has happened, include the victim's father Mr. Kentley and aunt Mrs. Atwater
(his mother is not able to attend). Also there is his fiancee, Janet Walker and her former lover Kenneth Lawrence, who was once David's close friend.
In a subtle move, Brandon uses the chest containing the body as a buffet for the food, just before their maid, Mrs. Wilson arrives to help with the party. "Now the fun begins", Brandon says when the first guests arrive.
Brandon's and Phillip's idea for the murder was inspired years earlier by conversations with their erstwhile prep-school housemaster, publisher Rupert Cadell. While at school, Rupert had discussed with them, in an apparently approving way, the intellectual concepts of Nietzsche's Übermensch and the art of murder, a means of showing one's superiority over others. He too is among the guests at the party, since Brandon in particular feels that he would very likely approve of their "work of art".
Brandon's subtle hints about David's absence lead to a discussion on the art of murder. He appears calm and in control, although when he first speaks to Rupert, he is nervously excited, stammering. Phillip, on the other hand, is visibly upset and morose. He does not conceal it well and starts to drink too much. When David's aunt, Mrs. Atwater, who fancies herself as a fortune-teller, tells him that his hands will bring him fame, she is talking about his skill at the piano, but he appears to think that it will be notoriety.
Much of the conversation, however, focuses on David and his strange absence, which worries the guests. A suspicious Rupert quizzes a fidgety Phillip about this and about some of the inconsistencies that have been raised in conversation. For example, Phillip had vehemently denied ever strangling a chicken at the Shaws’ farm, but Rupert has personally seen Phillip strangle several. Phillip later complains to Brandon about having had a "rotten evening", not because of David's murder, but over Rupert's questioning.
Emotions run high. David's father and fiancée are disturbed, wondering why he has neither arrived nor phoned. Brandon even goes so far as to play matchmaker between Janet and Kenneth, who rather resent this and increases the tension.
While leaving, Rupert is handed the wrong hat, with a monogram "D.K." (as in David Kentley) inside it. Rupert returns to the apartment a short while after everyone else has departed, pretending that he has absentmindedly left his cigarette case behind. He 'plants' the case, asks for a drink and then stays to theorize about the disappearance of David, encouraged by Brandon, who seems eager to have Rupert discover the crime. A tipsy Phillip is unable to take it any more, throwing a glass and saying: "Cat and mouse, cat and mouse. But which is the cat and which is the mouse?"Mr. Kentley decides to leave when his wife calls, overwrought because she has not heard a word from David herself. He takes with him some books Brandon has given him, tied together with the very rope Brandon and Phillip used to strangle his son; Brandon's icing on the cake.
Rupert lifts the lid of the chest and finds the body inside; his two former students have indeed killed David. He is horrified, but also deeply ashamed, realizing that they used his own rhetoric to rationalize murder. Rupert seizes Brandon's gun and fires several shots into the night in order to attract the police.
