65 million years ago, on the planet Somaris, pilot Mills (Adam Driver) convinces his wife Alya (Nika King) that he should take on a two-year space expedition to earn the money needed to treat their daughter Nevine's (Chloe Coleman) illness. Mills will earn thrice his normal salary for this expedition. During the journey, his spaceship, the Zoic, is hit by a mass of asteroids and crash-lands on an alien planet, which unbeknownst to him, is actually Earth. All the passengers were in a Cryogenic induced sleep and Mills was the only being awake as the pilot of the ship.With his ship damaged beyond repair, he finds that his passengers have been killed and contemplates suicide until he finds a lone survivor, a young girl named Koa (Ariana Greenblatt). Mills sends a distress beacon for rescue and decides to take care of Koa. However, they have difficulty communicating due to differing languages and a broken translator. Mills surveys the area surrounding the ship and finds skeletons of dinosaurs and steam jet geysers.Mills later discovers a functioning escape shuttle from the Zoic has landed on top of a mountain, 15 kilometers away. To encourage Koa to follow him, Mills lies about her family being atop the mountain, when in reality they perished in the crash. The pair quickly realize the planet is home to dangerous and aggressive alien creatures, which turn out to be Earth's dinosaurs. As Mills protects Koa, they begin to bond. Mills has a device that tells them what is safe to eat. Mills finds some poison berries that he stops Koa from eating.Koa watches several video messages sent by Nevine. The two are attacked by an unidentified monster, which Mills manages to wound before hiding in a cave. An insect gets into Koa's mouth and starts to suffocate her, but Mills finds it in time and extracts the insect. They are pushed deeper into the cave by a T-Rex who attacks them from outside the cave. Mills manages to injure the creature with his gun. Mills hands a few bombs to Koa, just in case she finds herself alone.They enter a narrow shaft to escape the cave. After a rockfall inside the narrow shaft separates them, Mills is trapped inside the cave, while Koa falls outside the cave system into the open jungle. Koa finds a large dinosaur tooth lying in the jungle, which is also very sharp. She laces the tooth with a paste from the poison berries. Mills is attacked by an Oviraptor and Koa is attacked by a raptor-like creature which she traps in a fallen tree log; she uses bombs Mills had given her to kill the dinosaur.Mills kills the Oviraptor with his gun and escapes the cave, however he falls into quicksand while searching for Koa. Koa rescues him and they continue up the mountain. However, Mills discovers that a huge asteroid, the same one whose debris his ship crashed into, will strike Earth in less than 12 hours.The two reach the escape shuttle, but Koa is angry when she discovers that Mills lied to her. Mills opens up to Koa about losing Nevine, who had died of her illness while he was away, and promises to protect her. Upon learning rescue is on the way, the two board the escape shuttle, but the asteroid's debris causes it to fall down the mountain. The shuttle cannot launch as it is in the wrong position and facing upside down.Mills and Koa manage to fend off a pair of Tyrannosaurus Rex. Mills goes outside the shuttle as he finds a gun lying on the ground, but the gun wont charge and he has to hide inside the shell of his ship. Koa lures the T-Rexes away from Mills using a projection of Nevine from one of her videos. Mills uses the distraction to shoot down one of the T-Rex, but the other understands the ruse and attacks Koa. Mills charges his gun and shoots the T-Rex dead and saves Koa.But the same creature they injured earlier at the cave, which turns out to be an enormous quadrupedal Theropod, also attacks. Mills asks Koa to launch the ship, and runs away. Mills manages to lure it toward a large geyser while Koa stabs it in the eye with a large dinosaur tooth that she coated in poison berries earlier. The pair escapes just in time as the asteroid strikes Earth, causing a cataclysmic event and the extinction of the dinosaurs. With the pod set to meet up with a rescue vessel, the two relax and fly off into the stars.In closing titles, the evolution of Earth is shown, at the spot where Mills and Koa left, through an ice age until the present day.