HUMONGOUS

During Labor Day weekend in 1946, young Ida Parsons is chased into the woods and raped by a houseguest. Her dogs break out of their pen and attack and kill Ida's rapist.

In 1982, brothers Eric and Nick borrow their father's yacht to take their girlfriends, Sandy and Donna, and their sister, Carla, on a weekend outing to St. Martin Island. That night, Eric and Nick discover and rescue a shipwrecked fisherman named Bert. Bert was wrecked offshore Dog Island, the home of lumber baroness Ida Parsons, who has used her family fortune to hole herself up on the island for the past thirty-five years, only making two annual voyages to the mainland for supplies, and never speaking to anyone. Recovering from the onset of hypothermia, Bert tells a campfire story about the wild dogs which roam Ida's island, acting as her sentries.

Donna, Eric, Sandy, Nick, and Bert wreck their boat and wash up on Dog Island. Bert is wounded, and Carla is nowhere to be found. Nick wanders off into the woods, and is killed by a hulking figure. The next morning, Sandy and Eric go onto the island, hoping Ida Parsons will help them get back to the mainland. After they leave the beach, Bert goes into shock, and Donna tries to warm him. The same figure which killed Nick sneaks up behind Donna and Bert, hurling Donna against a rock wall and decapitating Bert.

At the center of the island, Sandy and Eric discover Ida's fortified cabin. All of Ida's dogs are dead, their mutilated skeletons lying in their pens. In Ida's boathouse, Sandy and Eric discover Carla hiding under a tarp; she washed up at another point and made it to the compound during the night. Exploring Ida's compound, Eric, Sandy and Carla discover a dust-covered nursery full of antique toys, a crib, and Ida's diary, which contains insane, rambling passages about giving birth to a sick child, which she intends to keep sinless by secluding him from the evils of the outside world. Sandy comes across Ida's skeletal corpse in her bedroom. The group decides to collect supplies and escape from the island in Ida's old rowboat. While exploring the basement, they discover the corpses of Nick and Donna and flee to the beach in a panic.

Eric and Sandy deduce that Ida's 35-year-old mutant son is the one behind the murders, left insane by his life of solitude. With nothing to do but learn from Ida and explore the wilderness, he became immensely strong, a capable hunter, and is convinced that all outsiders are a threat to him and his mother. With the death of Ida, he was left without any basis for reality and ate the dogs to survive.

Eric and Sandy go back to the house and get the matches Sandy dropped. Ida's son attacks, breaking down the door. Eric fights using a broken branch, but the mutant fatally breaks his back. He then chases Sandy upstairs into his mother's bedroom. She wraps a blanket around her head and, playing Ida, convinces the mutant to leave his mother's bedroom. When Sandy leaves, the mutant pursues her to the boathouse, where she runs headlong into Carla. The mutant grabs Carla and kills her. Sandy sets Ida's boathouse on fire; although severely burned in the blaze, he attacks Sandy, chasing her up a hill. She yanks a sharp signpost from the ground and impales him. Traumatized by the deaths of her friends and the killing she committed, Sandy sits alone on Ida's dock, strongly resembling a scarred and traumatized Ida.

The surviving teens discover the monstrous offspring's origin and face off against him in a final confrontation on the island.

The ending brings together the generational trauma and isolation at the heart of Humongous. The survivors confront not only a physical threat but the legacy of violence left behind by Ida Parsons and her attacker. The film closes the loop on its opening tragedy, suggesting the monstrous cannot be hidden forever, and those who stumble into the past's shadow may pay the price.