|“||Feast your eyes upon The Triangle of Terror!||„|
|~ Professor J.S. Heinrich Ibsen about the Triangle of Terror.|
The "Triangle of Terror" is the evil nightmare machine that brings people's worst fear to life. It is created and owned by the mad scientist named Professor J.S. Heinrich Ibsen.
Peter has a nightmare that he goes to school naked, before Judy wakes him up and points out that that was his third nightmare that week. The two decide to head to Jumanji to take Peter's mind off things and Peter gets the clue "what lies before your eyes is sure, reflection makes your vision pure" before the two are sucked into Jumanji again where they're immediately attacked by a giant cockroach. Judy is too frightened to run and after they're saved by Alan, he's forced to carry her away. On the way to Crystal Lake (which Alan believes might be what their clue references) Peter gets stuck in a tar pit and Alan falls in when he tries to save him, but Judy manages to pull them both out.
Peter initially believes that the pit ate his clothes, but Judy shows him it didn't and they head to Crystal Lake where Alan and Peter clean up. Judy and Peter realize the clue didn't refer to the lake as nothing happens, but Alan sees a vision of himself old before being attacked by two giant cockroaches and Judy freezes again. Alan carries her to safety and Peter attacks the cockroaches with seashells and they suddenly disappear into thin air.
Peter realizes that Jumanji's playing tricks on them and that perhaps the "lies" part of their clue means lies as in a fib before he's snatched by a giant bird and taken to its nest. Alan rescues Peter from the nest, but the bird starts chasing them. They escape and realize that Ibsen must be behind what's going on so they head to his lab. In the lab, they search for anything that could have caused the weirdness and Alan finds a file on him on Ibsen's computer that reveals that Alan doesn't have a clue and is thus a permanent prisoner there and will grow old and die still stuck in the game.
Ibsen shows up and reveals he is responsible for what's going on as he's created a machine to bring nightmares to life, called "The Triangle of Terror". Judy and Peter escape the room, but Alan gets trapped in it. Alan gets out but sees a nightmare of Judy many years in the future leaving her daughter on her birthday to come with Peter to try to free Alan, but he's snapped out of it by Judy and Peter. He tells them they're going to solve their clue and he doesn't want Judy and Peter to return again before they're chased by a pack of jackals.
They escape across a bridge that Alan then destroys, but he ends up in another nightmare where he sees his own grave. After snapping out of it, he reveals what he learned to the kids, but Peter points out that that's Alan's fear and the machine just made him see that. They realize that confronting their fears make them disappear and head to Jagged Canyon where they figure out Ibsen's machine must be from his model in his lab. There they find it and plan to reflect the beams to cause a power surge and destroy it, but Ibsen shows up and powers the machine up to full, making all of their worst fears appear. Facing their fears doesn't work as these are actually real and Judy realizes that they have to destroy the machine to make them go away.
The three manage to climb the towers chased by their nightmares and reflect the energy beams into the center of the machine, overloading and destroying it. The nightmares disappear and the machine comes to life and chases Ibsen away. Peter realizes the clue referred to their manifested nightmares and by reflecting the beams and making the nightmares dissolve, they made their vision pure, solving their clue and sending them home. As they go, they promise once again to get Alan home and Alan's faith in returning home someday is restored after defeating his nightmare.