Tom Ripley is trying to survive in New York City. He has to rely on his wits while living off menial work. Between jobs, he engages in illegal scams and lives among shady people. One day, wealthy Herbert Greenleaf approaches Tom—who casually knows his son Dickie—to persuade him to travel to Italy and convince his wastrel son to return home. Tom eagerly accepts Mr. Greenleaf’s offer of a round-trip ticket and six hundred dollars in spending money. Arriving in Mongibello, Tom runs into Dickie and Marge on the beach; the couple seems indifferent to him until Tom tells them the truth about why he is there and keeps them entertained. Dickie invites Tom to share his luxurious house. Tom accepts, to the chagrin of Marge, who lives separately and sees Tom as an impediment to her romance with Dickie.

Tom and Dickie, who resemble one another, become fast friends and travel widely together, usually without Marge. They run into Freddie Miles, a wealthy acquaintance of Dickie who reminds his chum about a scheduled winter skiing party in Cortina. Tom, thrilled to be living a leisurely life he could only dream about before, covets Dickie’s fine clothes, expensive possessions, and a monthly allowance of five hundred dollars.

The friendship between the two men becomes strained after Tom is discovered wearing Dickie’s best clothes, admiring himself in a mirror. Dickie cruelly repeats Marge’s suggestion that Tom might be homosexual; Tom hotly denies it. The friendship crumbles further after Tom attempts to involve Dickie in a drug-smuggling scheme. Dickie begins to spend more time with Marge and shuns Tom; Tom daydreams about eliminating Dickie. Because Marge is busy working on a book, Dickie consents to accompany Tom to San Remo. There, they rent a small motorboat and head into the Ligurian Sea. While they undress to swim, Tom beats Dickie to death with an oar, sinks his body with the anchor, and scuttles the boat near shore.

Tom returns to Mongibello. He tells Marge that Dickie has moved to Rome and is gathering his belongings. Tom reinforces his story by forging letters from Dickie to Marge and the Greenleafs, writing on Dickie’s distinctive typewriter and in Dickie’s style. In Rome, Tom forges Dickie’s signature to collect his monthly allowance. He wears Dickie’s clothes as he travels to France on Dickie’s passport. Back in Rome, as Dickie, he rents a plush apartment, knowing that wealthy Americans are exempt from reporting changes of address, and lives in quiet comfort, traveling whenever and wherever he pleases.

Freddie Miles, however, tracks down the apartment Tom has rented and shows up unannounced. He sees Tom, dressed in Dickie’s clothes and wearing Dickie’s jewelry, and grows suspicious. Before Freddie can do anything, however, Tom bludgeons him to death with a heavy ashtray. That night, Tom half-walks, half-carries the corpse downstairs and stuffs it into Freddie’s sports car. Tom leaves the body at a cemetery, where it is discovered the following morning.

For days afterward, Tom plays a dangerous game with the police—who are investigating not only the murder of Freddie but also the disappearance of Tom Ripley—with Marge, and with other acquaintances. He continues to impersonate Dickie, and, before disposing of Dickie’s typewriter, he composes a will. In it, Dickie leaves everything he owns to Tom. When Marge shows up at the apartment, Tom plays himself, the concerned friend. Tom claims to be living with Dickie and pretends to be bewildered by events. As soon as Marge leaves, Tom flees town, moving to Venice. Finally, it becomes too risky to continue playing Dickie, so he reverts to Tom Ripley...