He is portrayed by Dennis Quaid.
Payton is a calm lieutenant who awakens from hypersleep to find himself onboard an unknown spacecraft, along with another man named Corporal Bower. They both suffer from amnesia due to being under anesthesia during their hypersleep, and they begin working together to try and discover where they are and what they are doing there. It is revealed that the spacecraft had been carrying a large group of 60,000 people on a 123-year trip to another planet named Tanis, which is very similar to Earth, in order to establish a new colony of humans since Earth is now incredibly overpopulated and resources are scarce. Payton and Bower had been amongst those onboard the craft, and they soon come under attack from strange humanoid cannibalistic beings. As Payton is trying to access the bridge, he is surprised by a strange young man named Corporal Gallo, who is in a severe state of shock and states that the ship is lost in space.
Gallo has now overcome his shock and claims he had to kill his rotation team in self-defense because they developed Pandorum after Earth mysteriously vanished. Gallo speaks with gruesome fascination of Pandorum, provoking Payton into developing its early symptoms. He attempts to silence Gallo, who then grows insolent and continues to provoke Payton. At the same time, Leland invites Bower's team to dinner, and shows them mural drawings depicting the true story of Gallo's past and tells them what he heard from other passengers. Gallo developed Pandorum when the ship received news of Earth's disappearance, as did any humans that he brought out of hypersleep. Gallo then manipulated the other psychotics into exiling themselves within the massive ship to play a game which involved fighting, capturing, torturing, and eating each other. Eventually Gallo went back into hypersleep, leaving the descendants of the psychotics to evolve over the course of successive generations into the humanoids who continue the game Gallo started with their ancestors. Their mutation is due to an enzyme given to the humans members in hypersleep that was supposed to both help their bodies adjust to the conditions on Tanis and speed up evolutionary ecological selection. Instead, they ended up adapting to the completely artificial conditions of the ship's environment, becoming a troglofauna species as a result.
Later on, Payton and Bower's memories return and it is revealed that Gallo is actually Payton's former self, and that he's been hallucinating throughout the story. Payton tries to convince Bower that they must live out their primitive lifestyle onboard the spacecraft (which is revealed to be deep under the sea) to replace humanity since it caused overpopulation in the first place. Bower opposes Payton's views and they fight, eventually causing a window to shatter and water to poor into the cabin. Bower manages to escape, while Payton and the humanoids drown in the ensuing flood.