Billy Halleck is an obese, upper class lawyer living with his wife Heidi and their daughter Linda. Billy recently defended an underworld crime boss named Richie "The Hammer" Ginelli in court and is now celebrating his acquittal on a murder charge. Heidi, in an attempt to persuade him to forget about his obsession with food, attempts to give Billy oral sex as he is driving. Distracted, Billy accidentally runs over a Gypsy named Suzanne Lempke. He is acquitted in the subsequent proceedings by his friend Judge Cary Rossington. The localpolice chief Duncan Hopley also obstructs the case by committing perjury for Billy. Outraged by the injustice, Suzanne's father, Tadzu Lempke, places a curse on Billy on the steps of the courthouse by touching his face and uttering "Thinner". Soon afterward, Billy begins to lose weight rapidly, despite not working out or sticking to his diet. Heidi, fearing the weight loss may be due to cancer, calls Dr. Mike Houston, with whom Billy soon begins to suspect his wife is having an affair. Billy learns that Rossington and Hopley have also been cursed; Rossington has been metamorphosed into a lizard-like being, while Hopley develops purulent ulcers on his face and hands. Both Rossington and Hopley commit suicide. Billy tracks down the Gypsy camp and tries to reason with Tadzu; however, Tadzu is further angered and he makes the curse on Billy worse. Gina, Tadzu's great-granddaughter, uses her slingshot to shoot a large ball bearing which goes directly through Billy's hand, infuriating Billy into vowing revenge against Tadzu and the other Gypsies. Billy then enlists Ginelli to attack the Gypsy camp and persuade Tadzu to meet with Billy and lift the curse. Chanting a spell, Tadzu mixes Billy's blood into a strawberry pie. Tadzu states that if someone else eats the pie, the curse will kill them quickly and Billy will be spared. He urges Billy to eat the pie himself and die with dignity, but Billy refuses. Billy arrives home and gives Heidi the strawberry pie. She delightedly eats a piece, while Billy heads to bed, exhausted. The next morning, Billy finds Heidi's desiccated corpse next to him. He is gleeful to be free of the curse and of what he believes is his disloyal wife. However, when he goes downstairs, he discovers that his daughter Linda had eaten some of the pie for breakfast. At the same time, Billy also reads an article from the morning newspaper that highlights on Ginelli being found dead in New York City under mysterious circumstances. Wracked with guilt, he prepares to eat the rest of the pie. However, Billy is interrupted by Mike, who is at the door. Seeing Billy, Mike grows uncomfortable and struggles to explain his unannounced presence, somewhat confirming Billy's suspicions of an affair between Mike and Heidi. Billy invites Mike in for a piece of the pie and closes the door with a smirk.
Thinner received mostly negative reviews from critics. The film holds a rating of 15% on Rotten Tomatoes, based on 20 reviews. The critical consensus reads: "A bland, weightless horror film that seems to want to mock itself as the proceedings drag on." James Berardinelli gave the film two stars out of four, writing: "Thinner could have been an opportunity to examine the ethics of a slick lawyer who refuses to accept responsibility for his actions.... Unfortunately, questions of morality are of secondary importance to a film that emphasizes its Death Wish aspects." Owen Gleiberman of Entertainment Weekly gave the film a D rating, writing: "Like too many Stephen King movies, Thinner is all concept and no follow-through." A more positive review came from Mick LaSalle of the San Francisco Chronicle, who called Thinner "one of the better Stephen King-derived movies."
