Scott Westerfeld’s young-adult science-fiction novel Horizon (2017) is a survival story in the “lost world” literary tradition. After a plane crash over the Arctic, eight young survivors emerge from the wreckage to find themselves in a strange and hostile jungle governed by inexplicable physics and populated by bizarre creatures. Stranded and cut off from the known world, the teenagers must pool their varied skills to navigate their deadly new environment and unravel the mystery of their location. Horizon blends a fast-paced adventure plot with a high-concept scientific mystery that challenges its characters to adapt, innovate, and question their reality. The novel explores themes including The Engineering Mindset as a Survival Tool, Collaboration Over Hierarchy, and Crisis as a Revealer of Character.

Horizon is the first installment in a seven-book, multi-author series of the same name. It was conceived as a multimedia storytelling experience, integrating the novels with a tie-in video game to create a more immersive, narrative world. Westerfeld is a #1 New York Times best-selling author known for acclaimed series like Uglies and Leviathan.

This guide refers to the 2017 Scholastic Inc. hardcover edition.

Content Warning: The source material and guide feature depictions of illness, death, child death, and animal death.

Plot Summary

Javier “Javi” Perez and his fellow Robotics Club members from Brooklyn Science and Tech—team leader Molly Davis, Anna Klimek, and Oliver—are on Aero Horizon Flight 16, bound for the Robot Soccer World Championships in Tokyo, Japan, with their adviser, Mr. Keating. Javi, a nervous first-time flyer, is distracted from his fear by Molly’s endless stream of airplane trivia. Also on the plane is Yoshi Kimura, a teenager returning to Japan after stealing his family’s priceless 17th-century katana, or samurai sword. He dreads the punishment awaiting him and quietly wishes the plane will never arrive.

Hours later, as the flight passes over the vast, icy expanse of the Arctic Circle, Molly dreams of a strange, lonely consciousness reaching up from the snow for the plane. She’s jolted awake by the shuddering of the aircraft, alarms shrieking as smoke fills the cabin. The oxygen masks deploy, and the roof of the plane is torn open to the sky. Anna watches in horror as a strange, lightning-like energy being moves through the cabin, analyzing the passengers. It seems to select some and reject others, ripping seats from the floor and flinging people, including Mr. Keating, out into the open air. Despite the catastrophic damage, the plane makes a controlled landing, coming to rest not in the Arctic snow but in a warm, alien jungle dominated by red-tinged plants.

The only survivors are Yoshi; an older, domineering teen named Caleb; two young Japanese sisters, Kira and Akiko; and the four members of Team Killbot. The other 500 passengers and crew have vanished. Caleb attempts to assume leadership, to the distaste of the other survivors. Yoshi retrieves his katana from the cargo hold and ventures into the jungle alone to find fresh water. As the others scavenge supplies from the wreckage, Anna discovers a strange, donut-shaped device with rings of symbols. When she twists it and presses two aligned symbols, it generates a field of low gravity. Javi, bouncing on an inflatable emergency slide, launches high into the air to survey the landscape. His aerial view is cut short when he’s attacked by a flock of aggressive, razor-beaked birds. Anna realizes that the birds are attracted to the device, and she manages to save Javi by briefly deactivating it. The group, worried for Yoshi’s safety, mounts a rescue mission.

Using the gravity device to perform massive, arcing jumps through the treetops, Molly, Javi, and Anna head in the direction where Javi saw a waterfall. They’re again attacked by the flock of birds, which Anna names “shredder birds,” confirming that the creatures are drawn to the device’s energy field. Forced to travel on foot, they reach the waterfall and are ensnared by carnivorous, animate vines. Just as the vines are about to crush them, Yoshi appears and frees them with his katana. He calls the plant “tanglevine.” The reunited group journeys back to the crash site. That night, while camping in the jungle, Molly uses the device to launch herself high above the persistent mist and confirms that they’re not on Earth when she sees two moons—one red and one green—in the sky. The next day, the survivors test local flora for edibility. Javi gets violently ill from green “pukeberries,” but Kira discovers that red “omoshiroi-berries” and blue berries are safe to eat. Oliver, distraught, finally forces the group to confront their denial and hold an impromptu memorial for Mr. Keating and the other passengers.

After the memorial, Caleb, an amateur astronomer, proposes using the gravity device to analyze the stars to confirm their location. In exchange, he wants the others to help him build a massive signal fire. They agree, using the device’s low-gravity effect to haul huge logs. Caleb is launched into the sky, but a sudden cold wind blows him far off course. The others see his emergency flare plummet. They follow his trajectory and discover a bizarre, perfectly circular patch where the plants are stunted and the air feels unnaturally heavy. Inside this high-gravity zone, they find Caleb, fatally crushed. As he dies, he gasps that the moons are fake and tries to say the word “Ursa.” That night, Yoshi and Kira sneak back to the high-gravity zone. Suspecting that another device is the cause, they dig at the circle’s center and unearth a second gravity device set to a high-gravity mode.

The next morning, an expedition party consisting of Yoshi, Anna, and Kira sets off with the new device to investigate a strange radio signal that Yoshi heard near the waterfall. Meanwhile, Molly, Javi, Oliver, and Akiko experiment with the original device’s other settings. After discovering a setting that can supercharge electronics, they attempt to power the plane’s long-range radio but accidentally restart one of the jet engines. The damaged engine catches fire, triggering a massive explosion that destroys the remains of the aircraft. They barely escape, but their shelter and most of their scavenged supplies are lost. The explosion attracts a giant, flightless bird with a razor-sharp beak. In the ensuing fight, Molly is slashed by the bird’s claw, which leaves a glowing green, poisonous substance on her shoulder before Yoshi scares it away. Molly’s condition rapidly deteriorates, and she falls into a feverish state.

Far away, the expedition party uses their device to climb a massive, miles-high artificial wall behind the waterfall. They discover a network of maintenance tunnels populated by small, eight-legged robots. The tunnels lead to a control room containing a vast three-dimensional model of the region, revealing that the jungle is just one part of a long rift valley. When Anna smashes one of the small robots, a larger security machine attacks them. In the fight, they use the gravity device to make the robot too heavy to hold its grip on a ledge, sending it off the cliff’s edge. The strain of the high gravity triggers an avalanche of snow from the top of the wall. With the sky cleared by the wind, they look out from a cave mouth and see the constellation Ursa Major, the Big Dipper, with the North Star directly above. They realize that Caleb was right: They’re on Earth, trapped in a hidden, artificially maintained valley in the Arctic.

The expedition returns a day early, guided by the smoke from the destroyed plane. They share their discovery: The technologically advanced group who built this protected Arctic valley is most likely based in a large structure at the valley’s far end, as shown on the model. The news rouses Molly from her delirium. The poison has changed her, giving her a strange new awareness of the valley’s flora and fauna, but she’s lucid and resumes command. She agrees that their only hope for answers and a cure is to journey to the other end of the rift. She believes that they were all chosen to survive the crash for a specific reason. With their camp destroyed and their food supply dwindling, the eight survivors unite. Leaving the wreckage of Aero Horizon Flight 16 behind, they prepare for the arduous journey into the unknown depths of the valley.