Roommates of a peculiar nature, John Brandon, and Philip, collude and conspire to strangle a mutual acquaintance named David Kentley. The weapon is a simple piece of rope. The temporary disposal location of the corpse is a simple luggage trunk. The duo will find a more careful and precise location for permanent disposal later, but first things first among the young offspring of the well-to-do: there’s a party to be planned!
Champagne flows as Philip joins Brandon in a toast to having pulled off people say cannot be done: committing the perfect murder. The dinner party that the two young academic phenoms have planned is no mere kegger. Among the guests expected to attend, include the parents of David Kentley as well as intended Janet Walker. The two have also sent invitations to the man Janet was planning to marry before she met David, Kenneth Lawrence. And, finally, the piece de resistance: Rupert Cadell, the housemaster of the prep school where they met as well as the man Brandon insists was the true inspiration for their act. John and Phillip have taken from what Cadell taught them one very important lesson that rises above all others.
Murder is a crime only for the masses of those who commit it, but for an elite intellectual few it is a privilege.
Mrs. Wilson has had her housekeeping labor stretched and enhanced by the two to include setting the table for the upcoming dinner. On an impulse—a trait that defines his very character to the bone—Brandon suggests what kick it would be if dinner were instead laid out on the trunk. As expected Mr. Kentley arrives for the party, disappointment is in the air. It seems that David’s mother won’t be eating dinner from atop the trunk inside which her sons lie murdered, after all. Since Mrs. Kentley is not feeling well, Mr. Kentley instead arrives with one Mrs. Atwater whom he introduces as his sister. Mrs. Atwater immediately confuses Kenneth with being David which causes the nervous Philip to break the glass in his hand. The rest of the guests quickly follow with Rupert Cadell being the late arrival.
From out of the blue, Philip asserts that his unwillingness to dine on chicken and Brandon fills in the gaps: his friend once had a job choking chickens and on one memorable occasion, a pullet thought dead suddenly seemed to resurrect back to life. Philip petulantly denies such a story could even be possible while Rupert expresses amusement due to his knowing it is absolutely factual. At this point, Rupert engages his professorial air to demonstrate why Brandon and Phillip might have learned that all-important lesson from him.
Murder, according to him, is an art and one that should remain in the exclusive domain of those superior enough to know how and when it should be utilized. David’s dad is moved to inquire how the superiority of those charged with such responsibility is to be decided. Brandon’s response is one that Kentley immediately recognizes as stemming from the philosophy of Friedrich Nietzsche. He then makes the usual point of those opposed to the idea that a superior intellect should not be bound to follow inferior moral precepts by reminding them that Hitler admired Nietzsche as well.
In a moment of confidentiality, Rupert seems to seriously inquire of Brandon is he is planning on committing a murder but receives no satisfactory reply. The party drones on as Mr. Kentley becomes more and more fidgety over David’s unexplained tardiness. Meanwhile, in the absence of David, Brandon appears to be trying to manipulate Janet and Kenneth back into a romantic dyad. Throughout the evening, Phillip’s brittle hold on his increasing anxiety becomes more and more tenuous. When Brandon goes so far as to hand over a bundle of books tied together with the very rope used to kill his son to Mr. Kentley, that tenuous hold nearly rips apart. Overseeing everything with his acute insight into human behavior is Rupert Cadell who recognizes in the unusual behavior of his two former students something distinctly more serious than it might appear to the others. Rupert suddenly begins a concerted effort to track down the whereabouts of the still-missing David. When the phones rings with Mrs. Kentley on the other end of line with the urgent information that he is not at home, either, everybody starts to take their leave.
Mrs. Wilson hands Rupert his hat, but he realizes at once that not only is the hat not his, its owner apparently has the initials D.K. Once alone again, Brandon and Philip argue when Philip admits to feeling fear, an emotional most certainly not at home within a superior being. The doorbell rings and Rupert enters upon the excuse of having misplaced his cigarette case. Almost immediately, Rupert starts to ruminate over the possibilities of what might explain the mystery of the missing David Kentley. He even goes so far as to begin reconstructing a hypothetical murder of the boy before quite casually extricating a piece of rope from his pocket. As he absently plays with the rope, Phillip finally loses his last remaining grip on what has passed for his superior sense of cool under pressure. Amid Phillip’s hysterics, Rupert discovers the hiding place of the strangled boy.
Brandon, however, retains almost all of his cool under pressure as he proceeds to explain to Rupert exactly why they chose David and why they killed him. Rupert, struggling hard not to demonstrate that he is completely aghast, explains that the two have utterly perverted his words to twist them into gaining a meaning he never intended. Rupert walks to window, fires a gun into the air and turns to wait with Brandon and Phillip for the police to arrive.