A school acquaintance named “Tom” (Alain Delon) travels from America to Italy with the task of bringing back the wayward son of a very wealthy man. "Philip" (Maurice Ronet), though, is content living it up with his girlfriend, "Marge" (Marie Laforêt), and has no plans to return to San Francisco with this “friend” he barely recognizes. For now, “Tom” seems okay being taken care of financially, but that arrangement begins to bother "Marge,” and also makes a fellow American, “Freddy” (Billy Kearns), uncomfortable, so “Tom” is frequently unsure of his place - particularly when they all go out on a yacht and he understands just how unstable things are. Aware of his weakness, he’s been observing his friend closely, trying to learn how to copy not only his actions but also his crucial signature on the checks that pay for their trips. When a chance arises, he escalates his developing skills in deception. The central question is whether he can successfully conceal his crimes and manipulations from "Insp. Ricordi" (Erno Crisa), who’s investigating. The filmmakers clearly appreciated Delon's youthful appearance, or more precisely, his striking eyes; however, here he provides a portrayal that relies not only on his good looks but also on his talent for portraying someone agreeable and charming while being completely dishonest. Patricia Highsmith’s narrative is full of unexpected developments, some humor, greed, and desire - it's also an intelligent story that keeps the audience guessing until the very end. The film boasts impressive production values; not in a flashy or extravagant way, but in a believable and somewhat disreputable manner, as their questionable actions are suggested rather than shown directly. It’s gripping and absorbing, and if you have the opportunity to watch it on a large screen to better appreciate the beautiful cinematography, then you should enjoy it.

Source on TMDB