Max Seed, a reclusive Sufferton resident who was disfigured in a school bus crash as a boy, begins a brutal spree in 1973, torturing and murdering people. He films some victims starving to death in his locked basement, and his body count climbs toward 666, casting a shadow over the town and those who dare cross his path.
In 1979, Detective Matt Bishop arrests Seed during a tense siege that costs the lives of five fellow officers. Seed is sentenced to death by electric chair and imprisoned on an island, where he mostly behaves—until he kills three guards who try to rape him, revealing the depths of his brutality.
On Seed's execution date, the electric chair fails to kill him after two shocks. Not wanting Seed to be released under a state law that would allow a survivor of three jolts of 15,000 volts for 45 seconds to walk free, the prison staff and the detective declare Seed dead and bury him alive in the cemetery. Seed digs his way out a few hours later and returns to the prison, where he kills the Executioner, Dr. Parker Wickson, and Warden Arnold Calgrove before swimming back to the mainland. The next day, while investigating the massacre, Bishop realizes Seed was responsible when he discovers the serial killer's empty cemetery plot.
Over several months, Seed kills dozens of people, with one long shot showing him beating a bound woman with a lumberjack's axe for five straight minutes, a brutal display that underscores the killer's relentlessness and the terror surrounding his name.
One day, a videotape showing Bishop's house is sent to the detective's office. Knowing this means Seed will go after his family, Bishop races home, finding his wife Sandra "Sandy" Bishop and daughter Emily Bishop gone, and the four officers guarding the house dismembered in the bathroom.
Driving to Seed's old residence, Bishop is lured into a basement room containing a television and a video camera and locked inside. The television turns on and depicts Seed with Sandy and Emily. Emily informs Bishop that Seed wants him to shoot himself, but Sandy tells him not to; Seed will kill them anyway. Bishop tries to bargain by having Seed shoot him, but Seed does not accept it and kills Sandy with a nail gun, prompting Bishop to shoot himself in the head, believing that doing so will make Seed release his daughter. Instead, Seed takes Emily to the room containing her father's corpse and locks her in it, leaving her to die. With the murderer's freedom secure, Seed continues his killing spree with no apparent end in sight.
