In 1999, Captain Petey Shelburn attempts to return a
wind-up drum-playing toy monkey at an antiques shop. Before he can do so, the monkey plays its drum, triggering a
chain reaction that ends with a
harpoon gun disemboweling the shop owner. Shortly afterwards, Petey disappears, leaving his wife Lois to raise their twin sons Hal and Bill. The twins later discover the monkey among their father's belongings and wind its key. That evening, while they are at a
hibachi restaurant, their babysitter Annie is accidentally decapitated by the chef. Hal is being bullied at school by a group of girls. They steal his pants, and next day they discover he has the monkey in his backpack and throw bananas at him. Hal comes home, tired of being bullied by his brother, Hal chooses to wind the monkey's key in the hopes it will kill Bill. Instead, Lois suffers an
aneurysm and dies in front of Bill. Hal disposes of the monkey before he and Bill move to
Casco, Maine, to live with their aunt Ida and uncle Chip. When the monkey mysteriously reappears at their new home, Bill winds its key, causing Chip to be trampled to death in a horse
stampede. The twins seal the monkey in its box and throw it down a nearby well, hoping it will remain hidden. Twenty-five years later, Hal, still paranoid and traumatized by his past, is estranged from his family, including his son Petey. His ex-wife, now remarried, plans to have her new husband adopt Petey, effectively cutting Hal out of Petey's life. After Ida dies in a freak accident, Bill contacts Hal for the first time in nine years, voicing his suspicion that the monkey has returned and insisting Hal drive to Ida's house to retrieve it. Hal believes it when a woman explodes after a motel pool is electrified. While inspecting Ida's house, her real estate agent Barbara reveals to Hal that over the week following Ida's death, a series of bizarre fatal accidents have occurred in the town. A shotgun later falls out of a closet, killing Barbara. Hal and Petey soon learn that Bill lives in town and has the monkey, having hired a local named Ricky to retrieve it. Bill, who knows about Hal's attempt to use the monkey to kill him, has been turning the monkey's key in retaliation, though the monkey has only been killing random people. Hal implores Bill to stop, fearing for his son's safety. As whoever turns the key is spared, Bill says he will stop if Petey takes over the task of perpetually turning the key in his stead; if Hal refuses, Bill threatens to keep winding the key until Hal is killed, no matter who dies in the process. Ricky, obsessed with the monkey, forces Petey at gunpoint to retrieve it for him at Bill's house. Bill instructs Petey to wind the key, and a swarm of wasps kills Ricky. When Hal enters the house, Bill, furious at the sight of his brother still alive, attempts and fails to force the monkey to drum without winding the key in a desperate attempt to kill Hal. In retaliation, the monkey drums uncontrollably, triggering widespread death and destruction throughout the entire town. When Hal confronts Bill, the latter finally gives up, and the twins apologize to each other and reconcile over their shared grief for their mother. Shortly afterwards, the monkey beats its drum one last time, and Bill is suddenly decapitated by a
bowling ball bearing Lois' name. Driving through the now-devastated town, Hal and Petey accept their fates as the monkey's owners and vow to prevent the key from ever being wound again. A pale black-eyed man riding a horse—implied to represent
the Pale Horseman—passes by and acknowledges them. Hal, determined to reconnect with his son, suggests they go dancing, as it is something Lois had loved, and Petey accepts. ==Cast==