In London, Marco, a young, arrogant art student from Kansas City, is friendly with Timothy, a medical student, and Sarah, his girl friend. Timothy is dominated by his beautiful mother, Carol, who is divorcing her husband. Marco tells Timothy, who he believes has a talent for art, that he is studying medicine only because his mother wishes it. Timothy makes a half-hearted attempt to free himself from his mother's domination, but she easily regains control. Marco finds a studio apartment, and Timothy pays the first 2 months' rent, planning to move in with his friend. Carol prevents the move, and Sarah, who has fallen in love with Marco, moves in instead. During a party at her weekend cottage, Carol becomes furious when she finds Marco and Sarah making love in Timothy's room, and she orders Marco from the house. Marco avoids Timothy after this incident, but he comes to Timothy's aid when the boy gets into a pub fight, and he thereby wins Carol's gratitude. Later, Marco tells Timothy that he is tired of Sarah and plans to break with her at midnight on the approaching New Year's Eve. On that evening he stops by Timothy's home to pick him up for a houseboat party they are to attend, only to learn from Carol, who is at home alone, that Timothy left earlier to warn Sarah of Marco's callous plan. Marco seduces Carol and then scornfully leaves for the party. He arrives drunk, accompanied by a streetwalker, and tells Sarah how he took Carol to bed. Timothy overhears and flees from the party, and Marco follows, trying to convince the boy he was lying. Timothy, enraged, knocks his former friend into the river. Marco drowns, and Timothy is arrested for manslaughter.
