The next day, as Yoshi and Kira practice flying with their new device, the group discusses their situation. Anna theorizes that the jungle is artificial, arguing that the local wildlife is perfectly adapted to the strange physics. She believes that they must find the engineers who built the place, likely beyond the waterfall. Suddenly, the foghorn-like cry that they’ve heard before sounds again, this time close and angry. A 12-foot-tall flightless bird with a razor-like beak appears.

To save the others, Molly distracts the bird with a flaming stick while Anna manipulates gravity. After they fend off the initial attack, Anna activates high gravity just as the bird leaps, causing it to crash into Molly and injure her shoulder. Anna then switches to low gravity, which throws the flaming bird and the survivors into the air. When gravity returns to normal, the bird is singed but ready to attack again. Yoshi intervenes, drawing his sword, and the creature retreats. Molly notices that her wound is full of a strange, glowing green liquid. She feels no pain, only exhaustion, and collapses. The next morning, Anna, Yoshi, and Kira depart for the waterfall, promising to return in three days with help.

The journey to the waterfall is arduous. After arriving, Anna and Kira bathe in the cold water. Yoshi gets only static on his radio. Anna worries about Molly’s strange wound, and they’re all unsettled by the distant cry of the giant bird. Using low gravity, they begin the difficult, near-vertical climb up the rock wall beside the waterfall. Hours later, they’ve climbed for miles high into the mist. A strong, cold wind blows Anna, who weighs little in low gravity, off the rock face. She’s saved only by the bungee cords connecting her to Yoshi and Kira.

The wind clears the mist enough for them to spot a cave. Inside, they turn off the device and rest. The cave is unnaturally warm, and Yoshi’s radio picks up a faint, repeating beep. As the night wind blows the clouds away entirely, they look out from the cave mouth, finally able to see the full landscape below them for the first time.

The remaining survivors have converted the plane’s first-class cabin into a comfortable fortress. Molly, looking pale, suggests that they experiment with the gravity device’s unknown settings. Worried but unable to dissuade her, the group discovers that combining the known gravity symbols with a new symbol allows them to control electricity. The “low” setting dims a flashlight, while the “high” setting makes it blindingly bright and recharges Oliver’s dead phone.

Realizing that they can power human technology, they decide to activate the plane’s long-range radio from the cockpit. They first try the “low tech” setting, but nothing happens. Molly then activates the “high tech” setting, and the cockpit instantly powers up with lights, screens, and alarms. Javi realizes that the pilots must have left the engines engaged. Before Molly can shut the device off, the plane lurches. Outside, Javi sees one of the jet engines spinning, throwing sparks as flames erupt along the wing.

As an explosion rocks the plane, Molly orders an evacuation. She retrieves the gravity device, fighting off a wave of dizziness from her injury. The remaining inflatable slide has been punctured by shrapnel, so Molly decides that they will use the device to fly down. They jump, but in the low gravity, they weigh so little that the suction from the spinning engine pulls them toward the fire. Javi resourcefully throws a heavy pillowcase and then a flashlight upward, using the force to push them safely to the ground.

The engine continues to pull them toward the inferno, so Molly activates high gravity to anchor them. However, she quickly realizes that the denser air is feeding the fire with oxygen faster. She quickly switches to the “low tech” setting, which causes the turbine to sputter and die. They retreat as the jet fuel burns out, leaving them without their shelter or supplies. In the darkness, Molly sees that her wound is now glowing a faint green.

From their cave high on the cliff, Yoshi, Anna, and Kira see the plane explode on the horizon. Kira is panicked for her sister, and Anna wants to return immediately. Yoshi refuses, arguing that a journey in the dark is too dangerous and that they must press on to find help.

A small, eight-legged robot emerges from a tunnel in the cave. It ignores them but seizes Kira’s flashlight and then the gravity device from Anna’s pack. Anna smashes the robot with her foot and recovers a warm battery-like component from its remains. When two more robots appear and begin dragging away their damaged companion, Anna attaches a bungee cord to the wreckage so that they can follow them. As they prepare to enter the tunnel, the wind brings the smell of burning jet fuel, and Yoshi fears the worst for his friends.

The trio follows the robots through a network of hot, narrow tunnels into a massive cavern filled with more maintenance robots and blinking orange lights. In the center floats a detailed, three-dimensional model of a long rift valley; Anna investigates and discovers that it’s not a hologram but is made out of aerogel. They recognize their jungle at one end, complete with a tiny representation of the burning plane. Yoshi concludes that their entire environment is a massive, artificial machine.

Feeling angry and hopeless, Anna wonders where the engineers are. She notices a large, city-like structure at the far end of the model, on the other side of the rift, and insists that they must get there to find help for Molly. Just then, a new, much larger robot with four legs and sharp pincers emerges from a tunnel. Anna realizes that it’s a form of security, concluding, “I think it’s animal control […] And we’re the animals” (224).

The large robot chases them through the tunnels. After Yoshi trips, the machine leaps over him, confiscating his dropped flashlight before continuing its pursuit. Realizing that the robot is programmed to confiscate their technology, Yoshi fears that it will take the gravity device—their only way down the mountain. He tackles the machine near an opening in the cliff, and both tumble over the edge. Kira catches Yoshi, and Anna helps pull him to safety.

The robot clings to the ledge by a pincer. To dislodge it, Anna activates high gravity. The machine’s pincers bend under the newly immense weight, and it plunges into the abyss. The sudden strain of high gravity on the mountain triggers a massive snow avalanche outside the cave. Afterward, the sky is clear, and Yoshi sees the Big Dipper—Ursa Major—and the North Star directly overhead. He realizes that this is what Caleb was trying to say: “Ursa.” As more robots approach, Yoshi knows they have to jump, now certain of where they are.

Molly has been unconscious since the fire, and her condition is worsening. The next night, the explorers return a day early, guided by a signal fire. Yoshi’s knee is injured from the fight with the robot. Javi recounts how their experiments led to the plane’s destruction and Molly’s collapse.

Anna and Yoshi explain what they discovered: They’re not on another planet but on Earth, in a massive, artificial rift valley near the North Pole. The jungle is a self-contained biome protected from the Arctic by heated walls. They describe the model they saw of the entire valley, which includes a large, futuristic building at the opposite end. They believe that the people who can help Molly are there. As Javi despairs over how to transport the gravely ill Molly, her eyes flutter open: “‘Simple,’ she says. ‘We fly’” (237).

Molly awakens feeling strangely altered, her senses heightened. She looks at her companions with a new, sharp clarity. She instinctively knows which berries are safe and understands that green things in this environment are dangerous. She tells the group that they must leave at once for the other end of the rift to find answers about the crash and why they were chosen to survive.

Yoshi and Anna agree, adding that the robots they encountered in the mountain may now be looking for them. Though exhausted, Molly accepts her role as leader. She understands that the journey will be long and that her friends will need her strength. Resolved and changed by her ordeal, she’s determined to get them all home.