In 1997, lonely thirteen-year-old Nicky stumbles upon Gorp, a bizarre, injured creature hiding in an abandoned treehouse deep in the woods. Frightened but fascinated, Nicky befriends the strange little monster and begins secretly caring for him.
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Thirty years later, Nick is a broken, self-destructive adult who returns to the childhood home left to him by his deceased parents. There, living with his older sister Barb and surrounded by remnants of the life he left behind, Nick begins to realize that Gorp never disappeared—and has grown into something enormous.Back in 1997, Gorp quickly becomes the companion Nicky has always wanted—loyal, funny, and completely devoted to him. Nicky eventually introduces Gorp to his best friend Luca, and the three spend an idyllic summer together. But as Gorp grows larger and more intelligent, his attachment to Nicky becomes increasingly jealous and possessive, driving a wedge between the two boys.
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When Nicky and Luca’s friendship begins to fracture, Gorp decides to protect Nicky in the only way he understands. Luca is murdered in cold blood, yet Gorp insists his death was an accident—that everything he has done has been for Nicky. Horrified by what his friend has become, Nicky
abandons Gorp and leaves behind the treehouse, the creature, and the trauma of Luca’s death.
 
In 2027 strange disappearances plague the neighborhood as Gorp emerges from the storm drains beneath the city. Nick is forced to confront the childhood he has spent his entire adult life trying to escape.As the situation escalates Nick finds himself facing another forgotten terror of his past: his childhood bully is now the deputy sheriff of Colorado Springs, Adam Knight. The coincidence of Nick’s return home and wave of violence is too much for the young officer to ignore. He begins to suspect, somehow, Nick is
responsible and vows to catch him in the act.
 
When Gorp abducts Barb, Nick descends into the
creature’s underground world to save her, ultimately
coming face-to-face with his long-abandoned friend.
What begins as a terrifying confrontation becomes
something more complicated: a reckoning between two
damaged friends who never stopped longing for each
other. Adam interrupts the reunion and the trio find
themselves in a fight to the death. In the struggle
Officer Knight is killed and Nick and Gorp are both
severely wounded. Nick and Gorp once again lean on each other for strength. Nick rides on the back of GORP back to the old treehouse, where the monstrous Gorp becomes
small again and Nick finally reconnects with the
friendship—and the part of himself—he left behind
decades earlier.