Dr. Ryan Stone (Bullock), a biomedical engineer from Lake Zurich, Illinois, is aboard the NASA Space Shuttle Explorer for her first space mission, STS-157. Veteran astronaut Matt Kowalski (Clooney) is commanding his final mission. During a spacewalk to service the Hubble Space Telescope, Mission Control in Houston warns the team about a Russian missile strike on a defunct satellite, which has inadvertently caused a chain reaction forming a cloud of debris in space. Mission Control orders that the mission be aborted and the crew begin re-entry immediately because the debris is speeding towards the Shuttle. Communication with Mission Control is lost shortly thereafter.
High-speed debris from the Russian satellite strikes the Explorer and Hubble, detaching Stone from the shuttle and leaving her tumbling through space. Kowalski, using a Manned Maneuvering Unit (MMU), recovers Stone, and they return to the Explorer. The pair soon discovers that the Shuttle has suffered catastrophic damage and the rest of the crew are dead. Stone and Kowalski decide to use the MMU to reach the International Space Station, which is in orbit about 1,450 km (900 mi) away. Kowalski estimates that they have 90 minutes before the debris field completes an orbit and threatens them again.
On their way to the International Space Station (ISS), the two discuss Stone’s home life and her daughter, who died young in an accident. As they approach, they see that the ISS’s crew has evacuated into one of its two Soyuz-TMA capsules. The parachute of the remaining Soyuz TMA-14M has deployed, rendering the capsule useless for returning to Earth. Kowalski suggests using it to travel to the nearby Chinese space station Tiangong, 100 km (60 mi) away, in order to board a Chinese module to return safely to Earth. Out of air and maneuvering power, the two try to grab onto the ISS as they fly by. Stone’s leg gets entangled in the Soyuz’s parachute cords and she grabs a strap on Kowalski’s suit, but it soon becomes clear that the cords will not support them both. Despite Stone’s protests, Kowalski detaches himself from the tether to save her from drifting away with him. Stone is pulled back towards the ISS, while Kowalski floats away to certain death. He continues to support her until he is out of communicating range.
Stone enters the space station via airlock of Pirs Docking Compartment. She cannot re-establish communication with Kowalski and concludes that she is now the sole survivor. Inside the station, a fire breaks out, forcing her to rush to the Soyuz. As she maneuvers the capsule away from the ISS, the tangled parachute tethers prevent it from separating from the station. Stone performs a spacewalk in order to release the cables, succeeding just as the debris field completes its orbit and destroys the station. Stone aligns the Soyuz with Tiangong, but discovers that Soyuz’s engine has no fuel.