KAPUKEA "KAPPA" GOODMAN (33) and MURDOCH "MU" GOODMAN (35) are professors navigating university politics on their way to tenure. One day, their spoiled son, XAVIER GOODMAN (7) sees a doll named BEAUREGARD with glowing red eyes in the window of a magic shop, and Kappa and Mu buy it for him, unaware that the doll is actually a conduit for ADRIAN (8), the son of SATAN. Adrian is hoping to earn his horns, but first he must convince a good person to commit a truly evil act. Beauregard, who speaks only to Xavier, quickly bonds with the child. Soon, Mu and Kappa, under Beauregard's control, leave their home in the middle of the night and brutally murder ZOE (20) and ZANDER (20), two underperforming university students. The couple wakes the next morning, disoriented, but with no memory of the events.
Meanwhile, Beauregard convinces Xavier to play sick and stay home from school, and Xavier spends the day wheedling his grumpy neighbor, RUDY RECK (40s), for permission to play with his friendly dog, HUNTER. Worried they're sleepwalking, Mu and Kappa visit a psychiatrist, CARL SIEGEL (38), who warns them Satan may be controlling them while they sleep and gives them a prayer to recite to keep evil forces at bay. Mu and Kappa recite the prayer, but it doesn't protect them from Beauregard's mind-control, and Mu and Kappa once again slip from their beds and murder Rudy.
Learning the prayer is only effective in the original Hebrew, Mu and Kappa once again recite the words the next night, this time successfully holding off Beauregard's influence. Angry, Adrian, through Beauregard, has Xavier prepare a sleep-inducing tea for Mu and Kappa the next night. The couple falls asleep without praying, leading to their murder of two other students, YANCY (20s) and YURI (20), and the accidental death of Carl.
Kappa and Mu adopt Rudy's dog, Hunter, for a delighted Xavier. Left alone at home, Beauregard taunts Hunter, and the dog eats him, leaving only the doll's red eyes in tact. The family races Hunter to the hospital, where emergency surgery is performed, saving his life. Mu and Kappa move Mu's elderly parents, RUTH GOODMAN (72) and ABE GOODMAN (75), into their home, and Mu keeps Beauregard's bejeweled eyes, storing them in a cabinet.
One month later, the family has settled back into a happy routine, and Mu learns he will receive tenure, since his class grade averages have increased with the murders of the lowest performing students. That evening, controlled by the glowing eyes of Beauregard, Mu, Abe, and Ruth all exit their beds in a trance, evil grins plastering their faces. A gleeful Adrian receives his horns from his proud papa, Satan.