The American Tom Ripley (Delon) has been sent to Italy to persuade his wealthy friend, Philippe Greenleaf (Maurice Ronet), to return to the United States and take over his father's business. Philippe intends to do no such thing and the impoverished Tom enjoys living a life of luxury, so the two men essentially spend money all day and carouse all night. Tom is fixated on Philippe and his girlfriend, Marge (Marie Laforêt), and covets the other man's life. Philippe eventually grows bored with his friend's fawning and becomes cruel and abusive to him. The final straw is when, during a yachting trip, Philippe strands Tom in the dinghy and leaves him to lie in the sun for hours.