Billy Halleck, a successful but obese lawyer, enjoys a privileged life with his wife Heidi and their daughter. One evening, Billy accidentally runs over an elderly Romani woman. In the courtroom, he uses his influence to get the charge dismissed with the help of his friend, the corrupt Judge Cary Rossington. The woman's father, an ancient Romani man named Tadzu Lempke, places a curse on Billy by uttering the word "thinner." As days pass, Billy notices he is rapidly losing weight despite maintaining his usual habits of eating excessively. Initially, Billy is thrilled, but he soon grows alarmed as he becomes dangerously thin and frail.

Desperate to reverse the curse, Billy seeks help from Doctor Mike Houston, who is having an affair with Heidi. With no medical explanation found, panic sets in as Billy suspects something supernatural. He reaches out to investigator Richie Ginelli, who promises to get to the bottom of the situation. As Billy's health deteriorates rapidly, he dives deep into tracking down Lempke and the Romani group to convince them to lift the curse. Along the way, he uncovers secrets that force him to confront moral questions about justice and revenge. The journey becomes more perilous as stranger events unfold, hinting at darker truths yet to come. With every passing moment, Billy races against time to save his life.