Astronaut Roy McBride undertakes a mission across an unforgiving solar system to uncover the truth about his missing father and his doomed expedition that now, 30 years later, threatens the universe.
In the near future, massive power surges start having devastating consequences around Earth. Astronaut Roy McBride is informed that his father, renowned astronaut Clifford, may still be alive after previously heading out into space for The Lima Project, which was meant to detect other intelligent life. Roy is tasked with finding Clifford after the Lima base was detected on Neptune.
Roy joins a crew to a base on Mars so that he may send messages to Neptune in an attempt to communicate with Clifford. He is taken off the mission when he tries to appeal to Clifford emotionally. The base’s director, Helen Lantos, shows Roy a video that reveals Clifford went mad on the base and killed his crew after they mutinied and tried to go back to Earth. Roy gets on the ship heading to Neptune, and the crew gets killed as they try to detain him.
Roy makes it to Neptune and finds the Lima base, which he plans to destroy with a nuclear payload. He finds Clifford, who still hasn’t given up hope that the project could be a success. As they try to head back, Clifford instead chooses death by drifting away from Roy into space. Roy carries on and destroys the Lima base, which helps him get back home.
Roy concludes that humans are the only intelligent life, and it inspires him to stay connected to those closest to him, including his wife Eve.
In the near future, the Solar System is struck by mysterious power surges, threatening all human life. After nearly dying from an incident caused by a surge, Major Roy McBride, son of famed astronaut H. Clifford McBride, is informed by U.S. Space Command (SpaceCom) that the surges have been traced to the “Lima Project” – created to search the limits of the Solar System for intelligent life, under Clifford’s leadership – from which nothing has been heard for sixteen years after reaching Neptune. Informed that Clifford may still be alive, Roy accepts a mission to travel to Mars to try and establish communication with him, joined by his father’s old associate Colonel Pruitt. It is shown in several scenes that Roy is very emotionally detached. He has no emotional reaction to his partner leaving him, or to the news his father may still be alive.
After taking a commercial flight to the Moon, Roy and Pruitt are escorted by US military personnel to the SpaceCom base, located on the far side of the moon. En route in lunar rovers, they are ambushed by scavenging pirates who kill their entire escort. Upon arrival at the base, a dying Pruitt is placed into intensive care. Roy transfers to the ship Cepheus, bound for Mars. The ship receives a distress signal from a Norwegian biomedical research space station. The Cepheus stops to investigate despite Roy’s protests, and Roy and the captain make their way to the station. It appears abandoned and the two split up, but Roy soon discovers an escaped baboon test subject feeding on the captain’s corpse. It attacks him when it notices his presence, but he manages to subdue it and lock it in another module. He then kills it instantly as it attempts to open the door, by depressurizing that module. Believing that he can save the captain, he tapes over the broken helmet visor of the captain’s space suit and carries him back to the ship, where he is declared to be already dead. A brief service is held where the captain’s body is ejected into space. Again, Roy appears to be very emotionless and calm after the violent encounter and death of the captain. He does admit that he experiences rage, and recalls his father expressing his rage.
Another surge hits as the Cepheus lands on Mars, requiring manual piloting to complete the landing. The interim captain freezes in fear, while Roy remains very calm and takes command of the ship, landing it safely. Roy is led to the underground SpaceCom base where he meets facility director Helen Lantos and is tasked with recording voice messages to send to the Lima Project in hopes that Clifford will respond. During one recording, Roy goes off-script with an emotional appeal to his father and is abruptly taken off the mission on the grounds of his personal connection posing a risk to himself and the mission’s success. From the startled reaction of the recording observation team to his emotional recording he assumes correctly that an immediate response from his father had been received and demands to hear it.
Sequestered in a “comfort room”, he is visited by Lantos, who reveals that she was born on Mars and was the daughter of Lima Project crew-members. She shows Roy classified footage revealing that Clifford’s crew had mutinied and tried to return to Earth, causing him to turn off their life-support systems, her parents included. She tells Roy that the crew that brought him to Mars are leaving to destroy the Lima Project station with a nuclear payload. The two decide that Roy should confront Clifford himself, and Helen sneaks Roy to an underground lake beneath the rocket launch site.
Roy clandestinely climbs aboard as the rocket takes off and is subsequently discovered by the crew, who is instructed to neutralize him. The entire crew is killed in the ensuing brutal fight. During the long journey to Neptune, a solitary Roy reflects on his relationships with his father and Eve, his estranged wife. The isolation and stress of the mission take a mental toll, but after several weeks he arrives at the Lima Project. While approaching the station in a shuttle attached to the Cepheus, the shuttle is damaged in a collision with objects in Neptune’s rings, preventing it from docking with the station. Roy enters the station via a space-walk while the shuttle drifts away. Finding the station abandoned and encountering the dead bodies of its crew, he plants the nuclear payload before encountering Clifford, the station’s sole survivor, who explains that the surges are coming from the ship’s malfunctioning antimatter power source, which was damaged in the mutiny. Clifford has continued to work on the project, refusing to lose faith in the possibility of non-human intelligent life.
After convincing Clifford to return to Earth, Roy finishes arming the payload and they climb out on the station’s surface in preparation for returning to the Cepheus. Clifford suddenly uses his spacesuit’s thrusters to launch the two of them off into space. With Clifford pleading for Roy to un-tether the two of them, Roy reluctantly does so and manages to propel himself back to the Cepheus using his own spacesuit and with a piece of the station’s hull as a shield against Neptune’s ring debris. Without enough fuel to return to Earth, he relies on the shock wave from the station’s explosion to gain the required speed. The data retrieved from the base suggests that humans are the only intelligent life in the universe, inspiring Roy to reconnect with those closest to him, and he returns to Earth with newfound optimism. After expressing his opinions in a psychological evaluation he reconnects with his estranged wife Eve.
The film opens with Roy McBride (Brad Pitt) delivering a video message for a psych evaluation. His voiceover states that he has always wanted to be an astronaut to help mankind. He goes to work on the International Space Antenna right above Earth. A massive power surge then hits the Antenna, causing it to come down violently, sending Roy and many other astronauts hurdling toward Earth. Roy manages to deploy his parachute, but it is damaged by the falling debris. He manages to land in a field and is found by onlookers before he loses consciousness.
More surges start happening across the planet. Roy is brought in to meet with his superiors at the U.S. Space Command. They discuss Roy’s father, renowned astronaut H. Clifford (Tommy Lee Jones), who left with a crew into space for The Lima Project, which was an effort to seek out other intelligent life across the Solar System. Clifford and his crew never returned and seemingly disappeared without a trace 16 years earlier. Recent readings have been coming from Neptune, indicating that Clifford may still be alive. Roy is instructed to take a top secret trip to Mars and send a message to try and communicate with Clifford. He accepts the mission out of integrity, and he looks back on video messages that Clifford sent him.
Roy is accompanied by Clifford’s old friend and associate Colonel Thomas Pruitt (Donald Sutherland) on their mission. They must first head to the moon and head for a ship that will take them to Mars. Pruitt suggests that Clifford may be hiding from them. Before heading off, Roy sends a video message to his estranged wife Eve (Liv Tyler). Roy and Pruitt join the crew on the moon, where they find themselves ambushed by space bandits. Most of the crew is killed, and Pruitt is severely injured. Roy manages to fight some off and get away with his life.
Before boarding for Mars, Roy is urged by Pruitt to succeed before he is brought to intensive care. Roy joins the Cepheus crew – Captain Lawrence Tanner (Donnie Keshawarz), Donald Stanford (Loren Dean), Franklin Yoshida (Bobby Nish), and Lorraine Deavers (Kimberly Elise) – as they head to Mars. On the trip, Roy asks for an update on Pruitt and learns he is about to undergo surgery. Roy also listens to a message regarding Clifford having disabled communications on Lima, which further stresses the need for the whole project to be shut down.
The crew receives a distress signal from a Norwegian biomedical research station. Roy heads over with Tanner to inspect it. It is empty, save for a baboon that was a test subject. It mauls Tanner and then goes to attack Roy, who manages to kill it by shooting it. Roy tries to get Tanner out, but another baboon attacks. Roy pulls himself and Tanner out and then depressurizes the chamber, causing the baboon to explode. Roy tapes up Tanner’s helmet and brings him back to the Cepheus, but he is already dead. The crew mourns Tanner and has a service for him before ejecting his body out into space.
As they continue the mission, Roy makes another psych evaluation video message in which he mentions the rage that he saw in the baboons reminded him of a rage he had seen in his father and in himself. Roy has always had something of a fear of Clifford, and he wishes to be nothing like him.
The crew arrives on Mars, but another pulse causes their ship’s systems to shut down. They manage to land their shuttle safely. They arrive at the SpaceCom station where Roy meets director Helen Lantos (Ruth Negga) before he is brought up by the station’s higher-ups. They bring Roy in to begin recording and sending messages for Clifford. He is meant to stress the urgency of the situation and the mission regarding his recovery. In a later recording, Roy delivers a more sincere message to Clifford, reminiscing about their time spent together when Roy was a child. However, the station chiefs take Roy off the mission, thinking the emotional message may compromise their progress.
Roy is placed in a comfort room where Helen comes to talk to him. She states that she was born there on Mars, and her own parents were part of The Lima Project, where they tragically perished. She asks Roy if the pulses are going to kill life on Mars and Earth, but Roy isn’t sure. Helen then shows Roy a classified recording that reveals the Lima crew mutinied against Clifford in an attempt to return to Earth, but he killed all of them and eventually went insane. She also reveals that the Cepheus crew is planning to blow up Lima’s base with a nuke. Roy thinks he should meet with Clifford directly. Helen guides Roy to the ship that will take off and helps him sneak onboard.
Roy makes it onto the ship as it is taking off. The crew catches him since they detect the break in the airlock. Deavers and Yoshida try to go after Roy, even as he insists that he is not a threat. The shuttle splits, causing Deavers to fly face-first into the door, killing her. Yoshida and Stanford then try to get Roy, but they end up suffocating. Roy takes command of the ship and heads to Neptune on his own. He is out there for several weeks, in which he thinks about Eve and Clifford, among other things.
Roy finally makes it to Neptune and finds the Lima base. He enters and finds the bodies of the crew before going to make his way with the nuke. He eventually discovers Clifford, who says he knew Roy would come. He explains to Roy that the surges are coming from the ship’s damaged antimatter source. Roy urges his father to go back home with him, but Clifford is still determined to prove that his project wasn’t a failure. He even tries to convince Roy to stay with him and continue the work together, but Roy is adamant in getting them both home.
Roy and Clifford start to make their way outside for Roy to go plant the nuke. However, Clifford attempts to pull them away by hitting his thrusters and propelling them away. Roy tries to pull Clifford back, but he is ready to die. Despite Roy’s best efforts, he cannot stop Clifford, and he watches as his father drifts into the abyss of space. Roy finds himself on the verge of giving up, but he makes it back to the base to plant the nuke. He then breaks off a piece of the hull to protect himself from the incoming rocks as he makes his way back to the ship. He propels himself there and boards the ship. As the Lima base explodes, Roy uses the explosion to help him make it back to Earth. His shuttle lands on a military base, and he is recovered by soldiers.
In one last video message, Roy reflects on what the mission proved to him, which is that it seems that humans are the only known intelligent life out there. It has inspired him to connect with those closest to him, including Eve. They are seen meeting up to get coffee. Roy closes his message by vowing to live and love from now on.