In the near future, a satellite capsule known as Pilgrim is coming back from Mars with soil samples
that will hopefully confirm the existence of alien life. Unfortunately the Pilgrim gets damaged by
asteroids and ends up veering off its course. Now the crew of the International Space Station must
intercept the Pilgrim and retrieve the sample. After helping Rory suit up for a spacewalk,
the rest of the crew rushes to their places to help Rory navigate through the rescue. Rory floats
outside to reach the station’s mechanical arm and guides it to catch the Pilgrim, which suddenly
comes at great speed and causes the whole station to shake when they make contact. For a moment the
crew worries something went wrong, but Rory reveals he’s successfully caught the Pilgrim.
Afterward, paralytic astrobiologist Hugh carefully begins testing the sample and is pleased to
discover an almost-fossilized single-cell organism in the soil. He tries to reanimate the organism,
but there’s no reaction, so he decides to mimic the atmosphere from proterozoic Earth by adding
a growth hormone. This time it does work and the organism starts moving, so the crew celebrates
having found the first proof of life beyond Earth. Soon the news outlets on Earth are covering this
amazing discovery, so the crew appears on TV to show their work in the station and how everything
works for kids to learn, including explaining how astronauts go to the bathroom. A particular school
has been given the honor to choose a name for the organism, and the kids decide to name it Calvin,
which is celebrated by a huge crowd on the streets. Sometime later, doctor Miranda checks
on David’s health as she expresses her concerns because David has been in the station for 473
days, which will soon become a new record. His atrophy has accelerated and he’s close to his
radiation limit, but David doesn’t care. After having been in the military and fought in the war,
David prefers to be up here where people aren’t nasty to each other. The next day,
Hugh discovers Calvin has grown very quickly and now it consists of hundreds of cells that are
developing a neural network. Each of these cells can perform functions independently,
which means each cell is simultaneously a muscle cell, a nerve cell, and a photoreceptive cell.
Commander Kat describes Calvin as being all brain, all muscle, and all eyes. Hugh notices that Calvin
is developing appendages so he tries to make contact, which successfully causes the cells
to move and take interesting shapes. Later while the crew has dinner, engineer Sho gets to watch a
livestream of his wife giving birth and meets his newborn daughter. The crew congratulates
him and Kat gifts him a book so he can do story time through video calls. After dinner,
David uses special software to check his body for any potential body problems, and Hugh checks on
Calvin again. The little guy is small but has a proper body now and climbs Hugh’s finger. A few
weeks later, the crew is shocked to suddenly hear an alarm coming from the lab. Rory rushes inside
and quickly takes care of the malfunction, but Miranda doesn’t understand how it could happen.
Hugh thinks he must’ve overseen something so Rory and Miranda immediately scold him, reminding
him to be careful because they don’t know what they’re dealing with. After a few more days pass,
Calvin has become completely inactive, and they think it may’ve gone into hibernation after the
change of air pressure caused by the malfunction. Miranda is relieved to see this because Calvin had
been growing too fast for her liking. While Calvin is inactive, the crew uses the chance to reinforce
the security in the lab, making sure it’s sealed off at all times. Later while Miranda is checking
on Hugh’s legs, he confesses he feels guilty over his mistake possibly having caused this on Calvin.
After they discuss some options, Hugh decides to stimulate Calvin with a very low voltage of
electricity to see if he’ll wake up. The first few tries don’t work, but suddenly Calvin jumps
awake and clings to Hugh’s hand as it breaks the electric wand. Hugh tries pulling his hand out of
the box, but Calvin is incredibly strong for such a tiny thing and the lower half of its body is
clinging to the box for extra leverage. Offering the wand again doesn’t distract it either,
and at that moment Calvin starts squeezing so hard that Hugh’s hand breaks into disturbing
shapes. The crew wants to enter the lab to help, but Miranda refuses because it would put them in
danger too. Suddenly Hugh’s head hits the box and he passes out as Calvin finally lets go of him,
so the crew can see how messy his hand is now. Then Calvin tests the glove and can tell it can’t
break it, so it grabs the electric wand and uses it to pierce the glove, allowing it to break free.
It immediately goes after the lab rat and brutally attacks it, devouring it in just a few seconds.
While Calvin is distracted with its meal, Rory uses the chance to enter the lab to rescue Hugh,
passing his body to his crew. However Calvin quickly jumps on Rory’s leg, so the crew has
to seal the lab again while leaving him inside. Then Rory grabs an oxygen candle and tries to
burn Calvin, who immediately jumps away and tries to hide. Kat gives Rory permission to kill the
creature, so Rory takes the incinerator and starts chasing the alien around the lab, but no matter
how many times Rory manages to hit it with the flames, it’s never enough to actually kill it.
Eventually Rory runs out of fuel and opens the container where Calvin hid last, only to find
it empty. Suddenly Calvin jumps on Rory’s face and enters his mouth, so now the crew has to watch in
horror how Rory is slowly killed from the inside until he’s only a floating body with blood flying
around him. To make matters worse, the incinerator also floats away and triggers the fire alarm,
so the suppressant gas starts to fill the lab. Calvin uses the chance to come out of Rory and its
size has become ten times larger. The crew rushes to close all the gas valves, but unfortunately
Calvin is faster as squeezes through one of the holes to escape the lab. Afterward, the team wraps
up Rory’s body and Kat sends a distress call to NASA, but Sho discovers that communications aren’t
working. It seems the transmitter is failing, so they have to go outside to fix it and be able to
contact Earth. Kat immediately suits up to go on a spacewalk, and when she reaches the transmitter
she discovers it’s overheated. Then she opens the coolant chamber only to find it empty, which means
Calvin must’ve eaten it. Suddenly the alien comes out of the coolant chamber and attaches itself to
Kat, looking for a way into her suit. Calvin is bigger now but the suit is still pretty strong so
it can’t break it. Kat closes the coolant valve and rushes back to the airlock, but as she moves
she discovers there’s liquid in her suit because Calvin has damaged her coolant tube. The liquid is
making it very hard to see, so she has no choice but to jump to reach the airlock faster. It’s a
risky move because she has to unclap, causing her to hit the station and roll around a bit until she
finally reaches the airlock. David quickly suits up too and rushes to help her, however Kat’s
helmet is filling with water and she’s already drowning. Wanting to bring Calvin down with her,
she grabs the airlock’s lever and holds onto it so David can’t open it. In a few more seconds Kat
sadly drowns, and the crew has to watch her body float away. Unfortunately Calvin catches on the
plan and jumps on top of the station before the body goes too far away. The crew cries for their
commander until Hugh reminds everyone they need to do something to keep Calvin out of the ship since
it’s obviously still alive and unaffected by the vacuum. Since the thrusters are the only way in,
they keep an eye on the temperature sensors to keep track of Calvin. Whenever the alien
comes close to a thruster, Sho turns it on to try to blast Calvin away, but all this
continuous blasting causes the station to shake and veer off course. Sho has no choice but to
use the remaining fuel to put the station back in orbit, which allows Calvin to sneak inside again.
Afterward Hugh proposes a theory: Calvin’s species must’ve dominated Mars for millions of years,
but it went into hibernation when the atmosphere of Mars collapsed. He thinks they should simulate
that same lack of atmosphere to force Calvin back into inactivity. The crew agrees and they
retreat to a capsule, sealing themselves off before expelling the oxygen from the
rest of the station. While they work on adding extra layers of sealing, Hugh is startled by
something in the shadows and starts feeling unwell. Miranda tries checking on him, but
he swears he’s fine. For the next few hours, the crew can only wait around. They grieve for their
lost friends and Hugh blames himself for what happened, but David says it was a team decision
to take Calvin. Then Hugh points out that Calvin is just a creature trying to survive and to do so
it must feed. At that moment Hugh passes out and the computers indicate his vitals are dropping,
so the others rush to stabilize it. While using the defibrillator, they notice something moving
on Hugh’s leg. They unzip the suit and immediately jump back to discover Calvin feeding on the leg,
Hugh never felt it because of his condition. Miranda tries using the defibrillator to shock
Calvin, but this only makes the alien float up and show how much its body has evolved.
The crew immediately rushes out and accidentally splits up, so Sho has to hide inside a sleeping
pod before Calvin can catch him. The creature tightly grabs the pod and tries to break it,
but it soon grows bored and goes away. Meanwhile David and Miranda return to Hugh, who doesn’t have
much time left. He asks his friends to lift him so he can feel what floating is like one last
time and then he dies. While the duo grieves, they see a beeping light on the screen and realize that
Calvin accidentally swallowed Hugh’s tracker, so now they can follow its position and make a
plan. Calvin moves around all over the station and eventually makes it back to Hugh, but while
it is devouring the body, it realizes it’s a trap right before David and Miranda close the door to
lock it inside. Then they purge the oxygen out of that room to try to suffocate it, which may take a
while. At that moment, the computer announces a shuttle is approaching them, and David realizes
Kat’s message did reach Earth. However the shuttle doesn’t get in contact with them,
instead it starts hitting the station. Miranda reveals that this is the last emergency firewall:
the shuttle isn’t here to save them, it’s come to push them into deep space so Calvin can’t reach
Earth. In the sleeping chamber, Sho also hears the announcement and thinks they’re being rescued,
so he gets out of the pod and leaves the hatch open behind him as he enters the docking area
to reach the shuttle. Miranda and David rush to try to warn him of the truth, but it’s too late:
Calvin sneaks behind Sho as he opens the hatch. With the shuttle leaving, the open hatch causes
the station to start decompressing and sucking Sho out while Calvin climbs his leg. Miranda grabs
Sho’s hand and tries to bring him back in, but Calvin continues to climb and reaches Sho’s arm,
so he lets go of Miran to stop Calvin from returning inside. Then Sho gets sucked into space,
but once again Calvin manages to cling to the station. It tries to grab onto Miranda next,
but she shocks it with a tool to push it away and joins David to make their way back inside,
closing the door behind them. When they look out the window, they discover the station is
falling apart and the breaking parts are crashing against each other for further destruction. Next,
David checks the computer and discovers they’re losing life support, not to mention temperature
and oxygen are dropping fast. He also notices that all this destructive chaos has pushed the station
into Earth, so they have about thirty minutes before they re-enter the atmosphere. Unfortunately
there’s no way they can survive re-entry, and they can’t reach the escape pods without Calvin
attacking them. As the duo comes to terms with their destiny and deals with the cold, they find
the book they bought for Sho’s daughter, so David decides to read it. When he says “goodbye, air”,
he gets an idea: since Calvin is searching for oxygen, they could lure it into an escape
pod using oxygen candles. David wants to launch himself with Calvin into deep space, which would
give Miranda the chance to reach a different pod and land on Earth safely. Miranda doesn’t like the
idea of a sacrifice, but David reminds her he’s a pilot and that he prefers space over Earth. After
they both suit up, David goes out on the corridors and begins dropping oxygen candles as he makes his
way to the escape pod. Calvin soon shows up and jumps from candle to candle as he follows David,
who quickly reaches the pod. As soon as he gets inside, Calvin jumps on him to hug him tightly,
so David distracts him with another candle and closes the pod hatch. Miranda notices this and
immediately rushes out to reach the other pod. The capsules soon disconnect from the station
and fly away, however the debris hits them both and causes them to start malfunctioning. While
Miranda struggles with her controls, David tries his best to keep his pod’s trajectory,
but Calvin grabs both his hands, causing him to scream in pain. After lots of shaky flying,
a pod flies off into deep space while the other lands in the middle of the ocean. Fishing boats
soon surround it to help, but as they open it, it’s revealed that David has made it to
Earth and Miranda is lost in space, meaning Calvin now has a whole planet to terrorize.