Life tells the story of the six-member crew of the International Space Station that is on the cutting edge of one of the most important discoveries in human history: the first evidence of extraterrestrial life on Mars. As the crew begins to conduct research, their methods end up having unintended consequences and the life form proves more intelligent than anyone ever expected.
The six-member International Space Station (ISS) crew capture a probe returning from Mars with a soil sample that might contain evidence of extraterrestrial life. Exobiologist Hugh Derry revives a dormant cell from the sample, and it quickly grows into a multi-celled organism that American school children name “Calvin”. After an atmospheric accident in the lab, Calvin becomes dormant. Hugh revives Calvin with mild electric shocks, but Calvin immediately becomes hostile and attacks Hugh, crushing his hand. While Calvin devours a lab rat and grows in size, engineer Rory Adams enters the room and rescues Hugh. However, Calvin latches onto Rory’s leg and Physician David Jordan locks Rory in the room to keep Calvin contained. After Rory unsuccessfully attacks Calvin with a flame thrower Calvin enters his mouth, killing him from the inside. Emerging from Rory’s mouth even larger, Calvin escapes through a vent. Hugh theorizes that lack of breathable air on Mars is what kept the organism dormant.
Finding their communication with Earth cut off, mission commander Katerina Golovkina performs a space walk to fix the antenna. Calvin attacks her outside the ISS rupturing her spacesuit’s coolant system in the process, causing liquid to fill her helmet. She refuses to open the airlock to seek help, keeping Calvin out of the station but causing her to drown in her spacesuit.
Calvin attempts to enter the station through the thrusters. The crew try to use the thrusters to launch Calvin into deep space, but their attempt fails and the station loses too much fuel. The ISS enters a decaying orbit, which will eventually cause the station to burn up in Earth’s atmosphere. Pilot Sho Murakami informs the crew that they need to use the remaining fuel to get back into a safe orbit, but the attempt would allow Calvin back into the station. The crew plan to make Calvin dormant by sealing themselves into one module and venting the atmosphere from the rest of the station.
When Hugh enters cardiac arrest, the crew realize that Calvin had attached itself to Hugh’s leg and was feeding off of him. Having grown into a larger tentacled creature, Calvin attacks the remainder of the crew. Sho seals himself inside a sleeping pod as Calvin attempts to crack the glass and get to him. David and quarantine officer Miranda North use Hugh’s corpse as bait to lure Calvin away from Sho and trap it in a module to deprive it of oxygen.
Having received a distress call prior to the damage to the ISS communication system, Earth sends a Soyuz capsule as a fail-safe plan to push the station into deep space. The capsule docks with the station and starts pushing it into deep space. Believing this to be a rescue, Sho leaves his pod and rushes to board the arriving ship, attempting to force open the capsule’s hatch. Once he opens the hatch, Calvin attacks him and the Soyuz crew. The crew tries to save Sho, but the encounter causes a docking breach that results in the capsule detaching and crashing into the ISS. David and Miranda, the only survivors, realize that the incident has again caused them to enter a decaying orbit. Aware that Calvin could survive re-entry, David recalls two escape pods, planning to lure Calvin into one pod and pilot it into deep space, allowing Miranda to escape to Earth in the other pod.
David leads Calvin into his pod and launches into space as Miranda launches hers. One of the pods hits debris and is knocked off course. Calvin attacks David as he struggles to send his pod into deep space. The earthbound pod performs a controlled re-entry and lands in water near two fishermen. As they approach the pod, it is revealed to be David’s, who is encased in a web-like substance. Meanwhile, Miranda’s navigation system fails and her pod is sent into deep space. David, still alive, tries to warn the fishermen not to attempt a rescue. The fishermen open the pod door as two other fishing boats arrive.