Nat and Pat are on a camping trip with their parents and older sister, Ginger. On their hike, the boys keep getting into arguments and Nat constantly disobeys his father's order not to climb the trees. When the Walds begin unpacking, Mr. Wald instructs Ginger to take her brothers for a walk around the forest. Ginger does, but the three quickly find themselves lost and in unfamiliar territory. Rather than a forest, they are now in an almost jungle-like area, with exotic plants and animals. The ground begins to rumble, and blue-furred beasts begin dropping down from the trees.
Ginger tries to get her brothers to stay quiet so they can get out without attracting the beasts' attention. However, on their way out, Pat ends up getting scared and runs off, separating the group. The beasts begin to close in on Ginger and Nat, before one of them taps Ginger on the shoulder and declares her "The Beast from the East". The beasts in front, who introduce themselves as Spork and Fleg, reveal that Ginger and her brother have been challenged to a game of survival. If Ginger is still It when the sun sets behind the Gulla Willow, she loses the game, and if she loses, she gets eaten. Nat and Ginger don't want to play, but the beasts force them to, and the game begins.
Along the way, Nat and Ginger find themselves faced with many dangerous obstacles, such as snakes and living trees. Nat suggests looking for a beast to tag, and when they do, they come across a large rock. When Nat touches it, the beasts appear and announce he's touched the Penalty Rock. This means he must be put inside the Penalty Cage, and eventually eaten. Ginger is left all alone, as Nat waits in the cage.
Ginger ends up tricking Spork into playing a game she and her brothers devised, and manages to successfully tag him. She runs off, and bumps into Pat, who's been looking everywhere for her and Nat since they got separated. Ginger fills him in on what's happened, and he initially doesn't believer her until the beasts appear, hunting them down. Pat and Ginger hide in a cave filled with bugs, and make their way to the Gulla Willow as the sun sets. However, Spork soon pops out and tags Ginger. She says this isn't fair, but he replies that since the game hasn't formally been declared over, the game is still on.
Pat and Ginger are carried off to a cooking pot, until Nat suddenly appears, revealing he managed to escape the cage. When the beasts see the identical twin boys, they are shocked. Fleg says she pulled a Classic Clone, something only Level Three players can do. Thinking Ginger and her brothers are higher level players, the beasts allow them to leave.
However, before they can leave, another beast appears. Ginger tries to get him to step aside, and says they're all Level Three players. The beast then reveals that he, too, is Level Three, and tags Ginger.
Nat and Pat are identical. They both have round faces and big, brown eyes. They both have brown hair which is parted in the middle, and straight on the sides. They both wear baggy clothes.
Nat and Pat often get into arguments and fights with each other, and never obey their father's commands. Nat likes climbing trees, and Pat is very stubborn. They tease and annoy their sister a lot, but they chose to trust her as they play the beasts' game.