Mary Jo Markey
In the near future, an unmanned space probe returns from Mars to Earth orbit with soil samples potentially containing evidence of extraterrestrial life. The probe is intercepted by the International Space Station, whose six-member crew retrieves its samples. Exobiologist Hugh Derry revives a dormant cell from the sample, which quickly grows into a multi-celled organism that American schoolchildren name “Calvin”. Derry realizes that Calvin’s cells can change their specialization, acting as muscle, neuron, and photosensory cells all at once.
During an experiment by Derry, Calvin suddenly becomes hostile, wrapping itself around Derry’s hand and crushing it. Calvin then escapes its enclosure and devours a lab rat, growing in size. Engineer Rory Adams rescues Derry, but Calvin grabs onto his leg, prompting physician David Jordan to lock Adams in the lab. After Adams unsuccessfully attempts to fight off Calvin, Calvin enters his mouth, devouring his internal organs and killing him. After several minutes, Calvin emerges from Adams’ mouth, larger than before, and escapes the lab through a fire-control vent.
The crew attempts to inform Earth of the situation, but the station’s communication system overheats, cutting off contact with Earth. ISS commander Ekaterina Golovkina performs a spacewalk to find and fix the problem, which turns out to be Calvin. Calvin attacks Golovkina and ruptures her spacesuit’s coolant system. As her suit fills with coolant, Golovkina makes her way to the airlock. She and the crew realize that Calvin will re-enter the station if they let her in, so she chooses to stay outside, and drowns in her spacesuit.
Calvin attempts to re-enter the station through its maneuvering thrusters. The crew fire the thrusters to blast it away, but they drain so much fuel that it causes the ISS to enter a decaying orbit, where it will burn up in Earth’s atmosphere. Pilot Sho Murakami suggests using the ISS’s remaining fuel to get back into a safe orbit even though it will allow Calvin to re-enter. The crew seal themselves in one side of the station and prepare to vent the atmosphere from the other side to render Calvin dormant. Unbeknownst to Derry, a paraplegic with no feeling below the waist, Calvin latches on to his leg and begins feeding off of him before the crew finishes sealing off the section where Calvin is supposed to be contained. The crew discovers Calvin feeding off of Derry after Derry unexpectedly dies. Calvin attacks the crew, forcing them to flee. Murakami seals himself inside a sleeping pod, while Calvin tries to break inside. Physician David Jordan and Quarantine Officer Miranda North use Derry’s corpse as bait to lure Calvin away and trap it.
Having received a distress call prior to the damage to the ISS communication system, Earth sends a Soyuz spacecraft to push the station into deep space. This is a fail-safe to protect Earth, but Murakami believes this to be a rescue and boards the Soyuz. He is followed by Calvin, who kills the Soyuz crew. A docking breach occurs, and Murakami sacrifices himself in an unsuccessful attempt to trap Calvin in the Soyuz. The Soyuz detaches and crashes into the ISS, causing the ISS’s orbit to decay again.
The remaining survivors, Jordan and North, speculate that Calvin could survive re-entry into Earth’s atmosphere, so they plan to lure Calvin into one of the ISS’ two escape pods. Once inside, Jordan will manually pilot the pod containing Calvin into deep space, thereby isolating it and enabling North to return to Earth in the other pod. Jordan leads Calvin into his pod and launches into space as North launches her pod, and the two pods go in different directions. As North’s pod flies in one direction, she records a black box message to warn Earth of Calvin’s threat. Subsequently, one pod is hit by debris, while Jordan is attacked by Calvin while trying to pilot. Eventually, one of the two pods lands in the sea and is found by Vietnamese fishermen, while the other pod flies away from Earth. What the Vietnamese fishermen find turns out to be Jordan’s pod. Meanwhile, North’s pod flies uncontrollably into deep space. On Earth, the fishermen open Jordan’s pod despite his warnings, as other boats arrive at the scene.