A chilling origin story unfolds around ten-year-old Timmy Reston, whose mother berates him for playing with a jigsaw puzzle of a nude woman. When she orders him to dispose of the puzzle, Timmy returns with an axe and brutally murders her, then dismembers the body with a hacksaw. The police arrive to find him hiding in a closet, pretending to be a witness to the crime. Believing his account, they place him with his aunt, and the community breathes a sigh of relief. Yet the past never truly rests. Forty years pass, and a sinister beacon from that old tragedy reappears when Timmy’s burned memory is stirred: a black-clad figure opens a box containing a photograph of Timmy’s mother along with her bloodied dress and begins to reassemble that same torn puzzle.
In a starkly different scene, a female student on the lawn of a Boston university is suddenly decapitated with a chainsaw by an unseen killer who steals her head. Lt. Bracken and his partner, Sgt. Holden, leap into a high-stakes investigation, navigating a campus shaded by fear and rumors. The academic world adds its own oddities, as Arthur Brown, a reserved anatomy professor teased for his sexuality, offers the detectives a guided tour of the school. The groundskeeper, Willard, is shown trimming hedges with a chainsaw, a detail that anchors the sense of imminent danger swirling through the campus.
Meanwhile, a student named Kendall receives a note from a female classmate asking to meet at the pool for a liaison, only to discover a cleverly staged decoy note that leads him to danger. The killer’s careful misdirection culminates in a shocking murder at the pool, where a victim is slain with a chainsaw, and the investigation tightens around who could know such precise timings. Willard is questioned and briefly becomes a suspect after a chainsaw is found near the victim and the torso is missing, underscoring how the killer’s methods cast suspicion far and wide.
To build a more effective profile, Dr. Jennings meets with Kendall at the station, while Bracken brings in an undercover officer and former tennis pro Mary Riggs to pose as a tennis instructor at the college, aiding Kendall with this delicate case. A journalist, Sylvia Costa, grows frustrated with the stalled progress, adding pressure for a breakthrough. That evening, the killer strikes again, stalking a student and severing her arms inside an elevator just as Kendall and the police arrive, and then stabs Sylvia to death on a waterbed, intensifying the campus-wide panic.
As the body count rises, one of Mary’s students, Suzie, becomes the killer’s next target and is viciously sawed in half in the locker room. Mary and Kendall attempt to disrupt the killer’s routines by turning off loud blasting music used as a diversion, but the killer slips away with Suzie’s legs. Kendall’s theory that the culprit is a faculty member gains weight when officials uncover that the dean has changed his name and that his mother was brutally murdered in the past; the trail leads to Timmy, the man now in charge of the restoration of order.
The tension peaks when Timmy drugs Mary at his apartment and tries to amputate her feet, hoping to force a fateful alignment with the crimes of years before—the pattern of victim selection and the killer’s insistence on body parts fitting a macabre reconstruction. Bracken, Holden, and Kendall storm Timmy’s residence, and the killer is fatally shot by Bracken as Kendall is rescued. In a final, unsettling twist, the recovered jigsaw puzzle in Timmy’s apartment reveals a gruesome living construction—a decomposing body made of pieces of Timmy’s victims, stitched into his mother’s dress. As the horrifying collage collapses onto Kendall, the chilling spectacle concludes with the jigsaw corpse coming to life and gripping Kendall in a brutal, surreal finish.
