Tom tries to appear casual as he returns to his hotel with Dickie's bloody clothes. He resolves to leave town as soon as possible, and, after briefly considering going to Paris, boards a train to Naples and then a bus to Mongibello. In Mongibello, Marge greets him as soon as he leaves the bus. She asks where Dickie has gone, and he tells her as casually as possible that Dickie will be in Rome for a week or so seeing art shows. Tom soothes Marge by giving her the bottle of cologne Dickie purchased for her and by telling her to write Dickie at the American Express in Rome. He also tells her that he will be meeting Dickie in Rome the next day, and they say a tense farewell. Tom then packs up as many of Dickie's clothes and documents as he can. The next day, Marge drops in and inquires as to why he is packing all of Dickie's possessions. Tom explains that Dickie has written him a letter, explaining that he will be moving to Rome and that he wants Tom to send his things along. Marge, who has of course not received any such letter, is visibly upset. Tom also checks the papers to see if his boat has been found, but sees no mention of it. He leaves Mongibello for Rome, shipping some of Dickie's things to Rome as well. He also writes a letter to Marge, impersonating Dickie. He tells Marge that he needs time alone and does not want to see her for some time, though he tries to do so gently. Finally, he buys some makeup in Rome to help him disguise himself.
In a hotel room in Rome, Tom practices pretending to be Dickie, but he also practices speaking as himself, because he is concerned that Marge or another acquaintance will find him and that he will have to suddenly revert to his own voice and mannerisms. He feels a sense of great calm and delight while imitating Dickie. He also picks up Dickie's mail from the American Express. Marge has written him a letter that expresses rueful, surprised acceptance of his decision to abandon her, and argues that Tom is a bad influence on him. Then Tom writes a letter, impersonating Dickie, to Mr. and Mrs. Greenleaf. The letter says that he is looking for an apartment in Rome while he trains under a painter called Di Massimo, and requests a few business-related documents from Mr. Greenleaf. Tom leaves for Paris soon after, in time for Christmas. He feels euphoric while he pretends to be Dickie in Paris, a city he has long idealized, and is proud of himself for getting invited to a party and making a good impression on his fellow guests. He wants to avoid letting anybody get to know him too well, so he wanders the city alone, listening to Christmas Eve carolers, distributing money to the needy, and enjoying a feeling of abundance and magnanimity. He leaves Paris and travels around France, in a haze of delight, before returning to Rome. He reads two letters from Marge, intended for Dickie. The first asks Dickie to spend time with her before she goes back to America in the spring. The second, which is short and blunt, informs Dickie that she will be returning home even earlier, in February. Tom worries that Marge will try to visit Dickie in Rome. He writes to Marge, as Dickie, and tells her that Tom has left and that he, Dickie, is still apartment-hunting.
Indeed, he does find an apartment to move into under Dickie's name, wanting to be able to tell people that he lives in Rome even though he plans on traveling much of the time. Tom decides to open an account under the name of Tom Ripley and occasionally siphon Dickie's money into it. He gets settled in Rome. His Italian improves, so much so that he practices making mistakes in order to sound more like Dickie, and he decorates his new apartment while cultivating a life of solitude. He only has one person over: an attractive young American man who leaves the country soon after. Since Marge continues to write Dickie, he sends a terse response, hoping she will get the hint and stop writing. One night, while Tom is packing for a trip to Naples, he hears the doorbell ring. The visitor is Freddie Miles, Dickie's friend, who says he has gotten Dickie's address from "an Italian fellow." Tom tells Freddie that Dickie has gone out for a long lunch, and that he is simply visiting for the day. However, Freddie notices that Tom is wearing some of Dickie's jewelry. Tom starts to worry that Freddie is growing suspicious—not that he has killed Dickie, but that he has become sexually involved with him. Freddie leaves and begins to speak with the building's superintendent, which Tom overhears. The superintendent reveals that Mr. Greenleaf has not left the building, and that there are no guests in Greenleaf's apartment. Freddie, growing more suspicious, returns to the apartment, clearly poised to question Tom. Tom, panicking, kills Freddie with a heavy ashtray. He then decides to make Freddie's death look like a drunken accident or robbery. He carefully makes a mess of the apartment, leaving various alcoholic drinks and cigarette butts all over the room. He waits for the sun to set so he can dispose of Freddie's body, using Freddie's parked convertible. He regrets having had to kill Freddie, but considers the death in a sense Freddie's fault, since his "dirty mind" and suspicions about Tom's sexuality rendered his death a necessity. Carrying Freddie's body, and hoping that the few passers-by they see will assume Freddie is merely drunk and unconscious, Tom climbs into Freddie's car and drives him to a remote old graveyard. There he abandons the body before driving the car to a random corner of the city and getting rid of Freddie's wallet, stealing some cash in the meantime.
The next day, Tom feels sick and hungover. The police call him, believing that he is Dickie Greenleaf. They tell him that Freddie's body has been discovered and that they want to ask him some questions in person. Tom is dismayed, since he plans on leaving for Majorca that day, but assents. While Tom waits for the police, his old Italian tutor Fausto calls for Dickie. He asks Dickie to meet him for lunch, since he is in town, Tom tells Fausto that he will come meet him, but doesn't leave the apartment. The police arrive, and they don't seem to think that Dickie is a suspect. However, they conclude that Freddie died only shortly after leaving his apartment, and therefore want to see if Dickie has any useful information for them. Tom informs them only that he and Freddie had a few drinks, but that Freddie seemed sober enough to drive. The police instruct Tom to stay in Rome, since they may want to question him further about Freddie. However, in the interest of avoiding other callers, Tom moves into a hotel room. He goes for a walk and reads the newspapers, all of which prominently feature Freddie's murder. They also name Dickie and give his address, though they do not refer to him as a suspect. He also gets a call from a man who identifies himself as Van Houston. Houston and Dickie clearly know each other, and it seems that Houston was traveling with Freddie. He is upset and wants to see Dickie, but, since both men have been forbidden to go out by police, Tom manages to avoid coming face-to-face with him.
That evening, Tom reads a few more newspapers, which reveal that several youths have been questioned as suspects in Freddie's death but let out of custody. What truly scares Tom, though, is a buried feature in one paper. The headline reveals that a boat with blood-like stains has been found, sunken, near San Remo. Tom is terrified that the police will trace the boat back to him and Dickie, and will recognize Dickie as Freddie's friend and the last person to see him. Then, he frets, they will either realize that Tom has killed Dickie or guess that Dickie has killed Tom— two equally disastrous outcomes. Unable to do much about this new development, Tom goes to the hotel clerk to see if there are any messages for him. Indeed there are several, from friends of Dickie and from Marge. Tom is afraid that Marge will come to Rome and find him, and resolves to get farther away as soon as possible, perhaps to India. He falls asleep and has a dream that Dickie has survived and is happily proclaiming "I swam!" Tom wakes, feeling unnerved and irrationally sure that Dickie is hiding in his hotel room.
After he returns to Mongibello and avoids Marge's suspicion with relative grace, Tom's plan seems to be going well. For one thing, nobody seems to suspect him or to think that Dickie is missing. He is living well off of Dickie's money and enjoying a life of travel and leisure. More importantly, though, Tom experiences a deep feeling of well-being. He does not merely imitate Dickie out of necessiry—he dives wholeheartedly into the impersonation, and derives great pleasure from the almost artistic pursuit of dressing, acting, writing, and painting like Dickie. He imagines that his feeling of satisfaction is similar to that which an actor feels when playing a role perfectly. This indicates that he enjoys the creative challenge of pretending to be another person. At the same time, Tom certainly likes pretending to be Dickie because it lets him escape himself. He feels charming, sophisticated, and generous, giving away lavish amounts of money and reveling in his ability to get invited to Parisian parties. And yet, with Tom, emotional highs are inevitably followed by equally severe lows. This euphoric period foreshadows a downward spiral.
In Shakespeare's Macbeth, another work of fiction about the aftereffects of passionate violence, the title character famously soliloquizes that “To-morrow, and to-morrow, and to-morrow / Creeps in this petty pace from day to day." Highsmith subtly references this line in chapter 14. Here, Tom thinks with great excitement about "tomorrow and tomorrow and tomorrow, being Dickie Greenleaf!" Though Tom's musings come in a moment of joy, this line hints at an eventual downfall, like Macbeth's. And indeed, such a downfall comes about thanks to Freddie Miles. Tom does not want to kill Freddie, and does not seem to particularly relish the act—while he is willing to commit violence, he always feels anxious in the moment. He kills Freddie solely because he is afraid that Freddie suspects him, either of having harmed Dickie or of being in a sexual relationship with Dickie. Readers will likely realize that another murder and cover-up pose a greater danger to Tom than Freddie's suspicions, but Tom is unable to think clearly. He is motivated at all times by a near-hysterical fear, and this fear leads him to commit murder rather than take a more rational path.
Ironically, Tom's fear-motivated violence is a kind of self-fulfilling prophecy. At the start of the book he is convinced that police are after him for his small-time scams. This exaggerated fear of pursuit, though, transforms into an entirely justified fear of pursuit after he commits a series of murders. In other words, the psychological sensation that he is being followed leads Tom to panic and commit increasingly prominent crimes, with the result that police (as well as friends and acquaintances) are far likelier to actually begin pursuing him. By the end of chapter 17, it seems that Tom simply has an unsustainable number of things to hide. He must avoid being connected to the boat in San Remo, must keep up appearances for Dickie's wide circle of friends and acquaintances, and must avoid becoming a suspect in Freddie's murder. Meanwhile, since he is now responsible for presenting himself as both Dickie and Tom, he is likely to draw twice as much attention—he now must avoid getting into trouble as either character, since any attention on Dickie Greenleaf or Tom Ripley is likely to bring his entire life crashing down.