In a rural Indiana neighborhood, Shaineh Berkowitz watches a daytime talk show on television. So entranced is she by the interview, that she fails to notice someone covering the home with termite tenting. A dark figure enters the kitchen and drops a white cake into a skillet, triggering a chemical reaction that produces a gaseous white cloud. Sensing a presence in the house, Shaineh investigates. Suddenly, a horribly disfigured, Frankenstein-like face emerges from the misty darkness. Shaineh gasps in horror.
Later, as the agents drive through the Indiana farmland, Scully reads aloud a letter addressed to Mulder. In it, Shaineh describes how, eighteen-years earlier, a presence entered her smoke-filled bedroom as, strangely, the voice of singer Cher filled the air. Three days later she woke up pregnant with her son, Izzy. Shaineh explains that she saw Mulder on the Jerry Springer show, and hopes he will investigate her case. The agents do, indeed, drive to Shaineh's home. There they discover a comic book bearing the exact likeness of the creature Shaineh claims attacked her. Shaineh explains the monster is called The Great Mutato, a creation of Izzy's fertile imagination. Izzy claims he, and many others in the community, have seen the creature--who apparently has a penchant for peanut butter sandwiches. Izzy and his friends lead the detectives to a wooded area, and using sandwiches for bait, lure the creature from its hiding place. The group gives chase, but the creature disappears into the darkness. Mulder then encounters an Old Man, who claims the real monster is his own son, renowned scientist Dr. Francis Pollidori. The agents visit Pollidori, who describes his experiments in genetic manipulation. He displays a photo of a fruit fly head... with legs growing out of its mouth. Later, Pollidori bids good-bye his wife, Elizabeth, as he embarks on a trip out of town. Moments later, termite tenting falls past Elizabeth's window.
When the agents stop by a country diner in downtown Bloomington, they are feted with heaping plates of food. It turns out that the entire town believes Jerry Springer will do a story on the creature... the result of a newspaper article in which Mulder is quoted as verifying the monster's existence. The agents realize Izzy secretly tape recorded their conversations.
As the agents drive along a country road, Mulder spots Pollidori's tented house. The pair race inside, where they discover Elizabeth's unconscious body. Shortly thereafter, the agents also lose consciousness. The Old Man, Professor Pollidori's father, steps from the smoke, a gas mask covering his face. When the agents regain consciousness, Elizabeth describes her attacker as a hideously deformed man with two mouths.
The Old Man brings the Creature a peanut butter sandwich as it watches the movie Mask, starring Cher, on television. Pollidori confronts his father, and in a rage, strangles him.
A mob of townspeople forms around the local post office as a mail clerk proclaims he's found the monster. He pulls someone wearing a rubber Mutato mask from the back room, then yanks off the mask, exposing Izzy. The postal worker then displays a box he intercepted, which is filled with identical masks.
Records indicate that the residue from the white cakes is a substance used to anesthetize herds of animals. Its use is monitored by the FDA, leading the agents back to the Old Man's farm. When the agents arrive at the scene, a diligent newspaper girl, who had been recording notes about the case, describes how she witnessed the creature burying the Old Man. Shortly thereafter, an angry mob makes its way towards the farm. The agents realize Pollidori killed his father. They befriend the frightened Mutato and attempt to escape, but they are spotted by the mob and retreat into a cellar. Pollidori and the townspeople burst into the basement. There, Pollidori claims the Creature was brought to life by his father. The Creature claims he never harmed another soul. He explains how, 25 years earlier, the Old Man realized his son was conducting secret experiments--of which he (Mutato) was an unfortunate product. The Old Man grew to love the Creature, and then set out to create it a mate. As the Creature continues his tale, the agents, putting together two and two, look around the cellar at the townspeople... one of whom resembles a horse, another a Billy goat and so on. The mob concludes Mutato is not a monster after all. A police cruiser transport Pollidori from the scene. The agents take the Creature into custody, but instead of transporting him to jail, they head for a Memphis nightclub, where Cher sings to Mutato, her biggest fan.