Plot summary
In 1980, advertising executive Vic Trenton's four-year-old son Tad died from dehydration after he his mother Donna were trapped in a broken-down car in Castle Rock, Maine, by Cujo, a rabid St. Bernard dog. The trauma of Tad's death led the couple to divorce; decades later they reconciled and remarried, but Donna died several years later from cancer. Shortly before her death, Donna seemingly saw, and spoke to, the ghost of Tad as an adult; Vic believes that Tad came to escort Donna into the afterlife.
In summer 2020, the now-retired Vic is weathering the COVID-19 pandemic in his friend Greg's McMansion on Rattlesnake Key on the Florida Gulf Coast. While walking, Vic encounters Alita Bell, an elderly woman pushing a large, squeaky-wheeled stroller with children's t-shirts on its seats. Alita introduces Vic to her four-year-old twin sons, Jacob and Joseph, who she seemingly believes are seated in the empty stroller. Vic, forewarned by his friend, humors Alita by pretending to see the boys. Several days later, Alita visits Vic to bring him cookies. During the visit, Alita claims the twins are playing in Greg's study; later, Vic is momentarily unsettled to see that a wicket basket containing the toys of Greg's cat has been upended. The caretaker, Mr. Ito, tells Vic that Jacob and Joseph died in the early-1980s after wandering out of Alita's garden and being bitten by rattlesnakes, with their father dying from a heart attack after finding their bodies. Following the twins' deaths, a posse drove the snakes to a shell beach at the north end of the island where they were wiped out.
While walking the following day, Vic finds Alita's corpse in her driveway next to the stroller; he summons the police, who remove the body and lock the stroller in Alita's garage. The next morning, Vic awakens to find the stroller in his house's courtyard. While pushing the stroller back to Alita's house, Vic inadvertently touches the t-shirts, causing him to have a vision of the twins' death. The police dismiss the appearance of the stroller as a prank. That night, Vic hears the stroller in his bathroom; when he enters the room, he sees the stroller with burial suits on its seats, and a bathtub full of rattlesnakes with a child's hand projecting and beckoning to him. Vic flees; when he finally returns, there is no sign of the snakes, but the stroller has moved to the courtyard.
The next day, while planning to flee the island, Vic is visited by Andy Pelley, a semi-retired police officer. Pelley provides more information on the destruction of the snakes; the majority were burned alive on the beach, while others drowned in a whirlpool while trying to swim to the neighboring island, Duma Key (which was later submerged by a massive tropical storm). Pelley instructs Vic not to leave the island, revealing that Alita made a new will and testament shortly before her death leaving all her assets to Vic; Pelley suspects Vic of coercing Alita into writing the will then murdering her.
Vic is stalked by the stroller and the ghosts of the twins, who telepathically urge him to "see us, roll us, dress us". Vic surmises that the ghosts were driven insane by their violent deaths, and are attempting to reclaim their childhood. He visits a gazebo at the end of the house's boardwalk, where he implores Tad to help him. Tad's ghost scratches the letters "PRA" on the gazebo's floor, which Vic interprets to means "pram". Reading Tad's message, Vic realizes how he can banish the ghosts. Vic pushes the stroller to the shell beach; during the trip, the twins grow suspicious. They attack Vic, first with a horde of spectral rattlesnakes, then with two living rattlesnakes, which Vic dispatches using Alita's snake-pole. Vic throws the stroller into the whirlpool, banishing the ghosts. He momentarily sees a vision of Duma Key above the waves, and an adult Tad waving to him.
Three years later, Vic is living in Newburyport, Massachusetts. Alita's autopsy and toxicology screening found no evidence of foul play, exonerating Vic, though Pelley continues to harbor suspicions against him. Vic ultimately inherits $4.5 million from Alita; he keeps $500,000 and donates the remainder to a food bank in Sarasota. As the story ends, a consortium of real estate agents is exploring plans to reclaim Duma Key via dredging; Vic believes that this will lead to the stroller being found, and fears that the ghosts of the twins might once again pursue him.
