The spaceship Odyssey 1 is travelling to Saturn’s moon Titan where they must collect natural resources for Earth. Since the journey takes multiple years, the crew sleeps for most of it and only wakes up every ninety days to do routine checks, maintenance, make sure the ship is on course, and report to Earth. After nine months, John wakes up as he hears all the usual warnings from the AI, reminding him that the medicine they use for hibernation may cause disorientation and nausea.
He tries to take a moment to recover, but Captain Franks tells him to get to work. After a quick shower, John joins Franks and Nash to check on the system. They get a message from Earth wishing them happy holidays and reminding them to get their psych evaluation.
John also checks his private inbox but he’s disappointed to find no messages. John starts thinking about his girlfriend Zoe and continues to do so during his psych evaluation. However when the computer asks him what he misses the most, he answers fresh air.
He then confesses to Nash that he forgot Zoe’s last name, but Nash tells him not to worry because it’s the expected confusion after waking up. Afterward John continues his maintenance work and remembers the day he met Zoe at a party, which helps him remember her last name. Now John feels much more relaxed.
Once all the work is over, the trio sends a message to Earth saying everything is fine and they go back to their hibernation pods. As John falls asleep, he remembers the day he saw Zoe the second time during a presentation about the Titan mission. The video showed how the ship would have to a do a slingshot maneuver around Jupiter that would launch them towards Titan.
The resources found there would be used as clean energy for Earth and fight against the damage humans have caused to the planet. The next time John wakes up, he makes sure to eat well and do some exercise. Later while he’s working, he hears a voice calling his name and starts following it, but finds nothing.
Suddenly the ship starts shaking and turning as the lights flicker. The AI sends a warning message before John watches some screws fall from the ceiling, leaving a panel shaking too. When he reaches out to touch it, the panel falls and hits him in the head, knocking him out.
John dreams of a crying Zoe before he wakes up, finding Franks and Nash checking on him. They said they don’t know what happened to the ship because John was the only one awake when it happened. When John enters the hole left by the fallen panel, he discovers various of the ship’s internal components received heavy damage.
Next the astronauts check the exterior video feeds and notice part of the hull was damaged as well, but they don’t find the moment of impact on the recordings and there are no error messages sent by Earth either. They reset the power and the system, but everything looks fine. Franks decides to go check the damage again while John records a message for Houston explaining the situation.
While doing so he remembers his next meeting with Zoe at a café and how she helped him with a videogame level he was stuck at. They ended up talking a lot and John shared how he had no family, which was why he had a good chance to be chosen to go to Titan. In the present, Franks points out that since everything is working well and there doesn’t seem to be any dangers for the crew, they should continue with the mission as planned.
Nash protests, saying it’s too early to tell, so Franks starts considering the possibility of the ship having structural stress that caused it to decompress. John refuses to believe it since Zoe was one of the designers but Nash runs with it, saying this could end up in an explosion when they do the slingshot. Frank tells them to work on repairs while assuming structural stress is what’s happening and once again announces they’ll continue as normal until they receive word from Earth.
While working, John keeps thinking of Zoe and the night he visited her at her home to finally have their first time together. He’s suddenly woken up by Nash, who still thinks flying on a damaged ship is an awful idea and they should abort the mission. At that moment the lights and screens flicker for a few seconds and quickly return to normal.
Nash runs diagnostics yet there’s no sign of power failure. They’re interrupted by Franks calling them to his office, revealing he heard their conversation. He points out that if they go back to Earth and Houston confirms there’s nothing wrong with the ship, they’ll be in big trouble.
Franks reminds them they must work together as a team and sends them back to their pods. John starts getting ready and remembers the morning after with Zoe, who said they should just be friends with benefits because he could be leaving soon. Nash approaches John again and tells him that instead of choosing ninety days of sleep, he should set eighty-nine days and twelve hours.
That way they can wake up before Franks and do the slingshot in the opposite direction to return to Earth. However John refuses, saying this is mutiny. A desperate Nash shares the story of a facility in Antarctica where the crew found a crack in the ice shelf that was making its way toward the station.
They wanted to evacuate, but their commander took out his gun and threatened to kill anyone who tried to leave. When the rescuers were sent later, the commander was nowhere to be seen and the rest of the crew had died from a shot to the head. In the end John gives in and says he’ll help Nash but only if they find evidence of more damage when they wake up.
As he goes to sleep with a new timer, John thinks about his last months on Earth, how he’d have nice moments with Zoe in private but would act professionally during lectures about Titan. The next time he wakes up, he thinks he sees Zoe inside the ship, but it’s just a hallucination. Soon Nash comes to check on him and John admits he’s seeing things, so Nash says it’s another reason to go home.
The duo goes to the bridge and find no message from Earth. They admire Jupiter’s beauty for a while and John announces he doesn’t want to follow Nash’s plan because there’s no evidence, triggering an argument. They’re interrupted by Franks, who had heard their plan and also set his pod to wake up early.
He sends Nash to work and when Nash tries to refuse, Franks whispers something in his ear that makes him leave the room. Afterward Franks asks John if they’re friends and shares a drink with him. He also promises that if actual evidence of danger is found, he’ll immediately abort the mission.
Meanwhile Nash is pacing nervously in the kitchen. When John comes in to have a meal, Nash stars harassing him and asking for backup. John continues to refuse and Nash loses his mind, yelling about the ship damage at the same time Franks arrives.
The captain wants to know if they can slingshot without Nash and John confirms they can because the math is in the computer, so Franks grabs Nash and tells him he’ll tell Houston about his subordination before sending him away. Afterward John goes through his day while still thinking of Zoe to the point he needs to take a break to brood in a dark room. Eventually he returns to the broken panel, which is now taped to the ceiling.
John enters the hole and finds many cables sparking. Suddenly a gadget starts failing, ejecting lots of sparks and all its screws. Then the damaged part of the hull cracks open and John has to hold on as space tries to suck him out, but he isn’t strong enough and his body floats away into the void.
At that moment he wakes up and realizes it'd been a hallucination. Franks announces it’s time to do the slingshot and Nash begs John not to do it, but he ignores him. As he makes his way to the bridge, John thinks of the time he and Zoe discussed moths and how flying toward the light is survival instinct.
Soon Franks and John are at the controls, but Nash is only allowed to watch. After lots of calculations and preparations, they start activating the thrusters and the ship flies around Jupiter. Suddenly the AI announces there’s a system overload, yet Franks tells John to keep going.
Inside the panel hole, the unit keeps on sparking. As the ship shakes like crazy, it finishes flying around Jupiter and John presses the button, pulling off the slingshot just in time. The maneuver is successful and the ship stabilizes with the system confirming they’re on course to Titan.
After celebrating with a drink, John does more exercise followed by maintenance work. He checks on the radios and hears a weird noise, so he puts his ear close and is startled by a voice yelling his name. He takes the radio to the other astronauts, who say they weren’t using the comms.
It could’ve been an echo, but the radar doesn’t show anything for a thousand miles. Nash says it was another hallucination and Franks announces it’s time to go back to sleep. This time John dreams about the moment he got a call confirming he was chosen for the mission.
However when he told Zoe, she didn’t look happy. She admitted she broke their agreement and fell in love with him, but John only replied this was bigger than them. A hurt Zoe confessed she voted against him because she didn’t want him to go, so John dropped his key and left.
The next time John wakes up, he feels dizzier than usual. He runs around the ship to clear his mind yet he can’t stop thinking about Zoe. When she suddenly appears nearby, John follows her while repeating that it’s just in his head.
He’s stopped by Franks, who tells him Nash found something in the reactor room and needs help. Franks is worried about John’s health and John snaps, yelling about the hibernation being torture. He calms down quickly and swears he’s fine, but Franks still reminds him that Zoe isn’t in the ship.
Then John joins Nash, who explains the reactor output’s starting to escalate. It appears to be minor, but they have to stop it from getting worse or they won’t finish the trip. Nash admits he isn’t feeling well so he asks John to double-check his numbers before presenting them to the captain.
John uses the chance to ask Nash why Franks knew he was hallucinating Zoe and Nash swears he didn’t say anything, only to have a breakdown as he doubts his own memories. Nash confesses he can’t remember his parents’ names or faces and John tries to assure him it’s just the side effects of the medicine, but Nash begins poking at his memories of Zoe and saying she may’ve found someone new. Josh pushes him back as Nash starts making weird noises, only for him to say they can still go back.
His anger growing, Josh gets more aggressive as he tells him to shut up, revealing that there are no numbers on the screen because Nash hallucinated them all. At that moment Franks calls them to the bridge and Nash still reports something wrong with the numbers. Franks shows them the screens and confirms the error, which they must solve to reach Titan safely.
He also reveals someone issued a low-level command to the reactor to cause these abnormalities on purpose. The last log-in belongs to John, but Franks thinks it was Nash using John’s password. Suddenly Franks takes out a gun and announces they’re going back into hibernation.
While John gets in his pod, he’s shocked to see Franks hitting Nash with the gun. The men fight for the weapon and Nash is pushed against John’s pod as Franks starts pounding his head with the gun. John can’t see the end because he falls asleep.
This time John dreams of the night before the trip when he visited Zoe to say goodbye. She apologized for everything and wondered if he ever loved her, but once again he avoided the question. The next time John wakes up, he’s feeling sicker than ever before and throws up as he has flashes of Franks killing Nash.
Before he fell asleep, it seems Franks asked him if they still were friends. John goes looking for the others and fails to find anyone until Franks surprises him from behind. The captain explains Nash was too unstable, so he just knocked him out to keep him in the pod until they reach Titan.
He refuses to put his gun away because he thinks John may lose it soon too. When John swears he’s fine, Franks explains Nash’s story about the Antarctica base had been wrong. The commander had told the crew to leave but they were too afraid and the commander left alone, so he froze to death.
The shots found by the autopsy had actually been self-inflicted. Franks announces the mission is still on and sends John to work. While checking the system, John feels something weird and checks his arm to discover his veins have acquired a dark color.
Suddenly his arm starts mutating and he yells in pain as his veins burst, ejecting great amounts of blood. However this also is a hallucination. At that moment John hears voices calling his name again but nobody is nearby.
Then John goes to the kitchen and Franks mention his hand is shaking before bringing up Zoe, but John tells him to stay out of his life. Franks decides to drop the truth: John never had a relationship with Zoe. She just kept approaching him on public spaces because the committee sent her to keep an eye on his mental health before the mission.
John freaks out and can’t understand how Franks can list all the occasions John met Zoe with creepy precision, so Franks points out he was in the committee too. Refusing to believe him, John walks away to work on the radio maintenance. He still thinks about Zoe, starting to doubt his memories now.
At that moment someone from Houston contacts him through the radio and asks a bunch of questions, but they can’t hear John’s answers and hang up. Then Franks calls him to the bridge and yells at him for believing he could contact Earth this far away. He plays the security footage to prove John had been talking alone and gets him to calm down by showing him how far they’ve come into space.
Refusing to be sent to hibernation again, John walks to another room and locks the door before Franks can follow him, demanding to see Nash. Franks says he can’t interrupt the sleep cycle and promises to take John to see him. However as soon as John opens the door, Franks pushes him against the wall and then to the ground, threatening to kill him if he doesn’t go to sleep.
Remembering what happened to Nash, John attacks Franks to disarm him and starts beating him up. A fight ensues as both men try to reach the gun and Franks almost chokes John to death, but John punches him to free himself. Next John grabs the gun and asks about Nash, only for Franks to laugh.
Feeling like he’s losing it, John wanders around the ship as memories flash in front of him and Franks’ voice haunts him. Not knowing what is real anymore, John is lost and confused, so Franks uses the chance to jump on him again. A new fight begins and John breaks Franks’ nose before hitting him with the gun, knocking him out.
Afterward John goes to bridge and uses the cameras to search for Nash to no avail. Franks appears behind him again and John pushes him off before furiously beating him up until Franks dies. Next John asks the AI where Nash is, and the AI says he’s alive on the bridge.
A confused John asks for the crew manifest and discovers that the crew is only one person: himself. His full name is John Franks Nash, and he’s been hallucinating the other two astronauts all along. Realizing he’s alone, John has a breakdown and considers self-deleting, but instead he goes to the radios and tries to contact Earth.
To his shock, Zoe answers. He isn’t sure if she’s real but he tells her everything about the other astronauts, admitting he may be going crazy. Zoe explains they’ve given him a larger medicine dose by mistake, which is why he suffers hallucinations.
She also confirms he’s the only crew member and drops a bigger reveal: the ship never left. John fell asleep before the launch and was put in a training facility in New Mexico. They built a perfect replica of the ship and put it one thousand feet underground to test the effects of hibernation and isolation on the human mind.
Zoe says she didn’t know either or she wouldn’t have let it happen. John mentions seeing Jupiter and the slingshot, but Zoe explains it was all a simulation. The incident that caused the damage to the hull and the panel had been an earthquake, which explains why he didn’t see anything on camera.
That earthquake cut all communications for a while and that’s why Zoe couldn’t call him before to warn him about the medicine. Now it’s finally over, Zoe tells him to simply walk through the airlock to find the rescue tunnel. John immediately gets ready to leave, only for Franks to appear again and tell him not to do it.
Franks insists the conversation with Zoe had been the actual hallucination because John’s mind was desperate for an explanation that made the situation make sense. However John refuses to believe Franks is real and opens the airlock anyway, saying he wants to go home. Franks walks away and John tells Zoe that he loves her before the AI opens the final door.
An underground tunnel awaits outside and John sees the fake ship above him. The area starts shaking as John hears voices promising to rescue him and machines digging into the ground. He climbs a ladder and yells to indicate his location.
At that moment a light flickers and when John touches it, he remembers the moth conversation about light. It turns out he truly is in space and his body is ejected into the void.
