After escaping a planet with an alien nest, the spacecraft Sulaco drifts through space while
its crew is frozen in hypersleep. Unfortunately there’s a stowaway alien egg on the ship that soon
hatches and causes an electrical fire. While the alien attaches itself to one of the crew members,
the automated systems send all the cryotubes into an escape pod and eject it into outer space. The
vehicle’s navigation system takes it to the nearest planet called Fiorina 161, an all male
penal colony populated by only the most dangerous criminals and owned by the same company behind the
ship. The inmates find the pod and discover Ripley is still alive, so they take her to the infirmary.
Doctor Clemens takes care of her and gives her an injection that helps her with the pain. He also
shares bad news: she’s the only survivor from the crash. The other two humans died and the android
was damaged beyond repair. Meanwhile the inmates use a crane to take the destroyed ship into the
building. Their dog Spike takes the chance to look inside and begins barking when he sees the alien,
which has gone unnoticed by the locals. Afterward warden Andrews announces to the prisoners that
they now have a woman in the building. Some of the men point out this will bring trouble,
but Andrew assures them he’s already talked to the company and asked for a rescue ship. Ripley is
left under the care of Clemens with strict orders of not leaving the infirmary until the ship comes
for her. Meanwhile Murphy checks on Spike and is shocked to see the poor dog has a bunch of wounds
on his head, which is strange because none of the prisoners would dare hurt him. Once Ripley is
feeling better, she demands to see the wreckage, so Clemens takes her there while explaining how
each person died. The little girl died in her sleep, but Ripley notices a scorching mark on
the side of the cryotube. Remembering the aliens have acid for blood, she gets suspicious and asks
to see the girl’s body. Next they go to the morgue and Ripley begins inspecting the little girl’s
body, wanting to be sure she doesn’t have an alien inside. Then she demands an autopsy under the
excuse of a possible infection, so a suspicious Clemens opens the body up. To Ripley’s relief,
the girl did die of drowning and there are no signs of alien life. At that moment Andrews comes
in and scolds Ripley for leaving the infirmary, but Ripley distracts him by asking him to burn
the bodies using the infection excuse. Moments later, the bodies from the ship are cremated and
inmate Dillon offers a very heartfelt eulogy. At the same time in another room, Spike starts
convulsing and suddenly explodes as an alien comes out of his body to then run and hide somewhere in
the building. Afterward Ripley washes up and shaves her head because it’s prison policy.
Then she goes to the mess hall and tries to thank Dillon for his eulogy, but Dillon warns her not to
befriend him because he’s done horrible things to women in the past. Ripley sits down and has
lunch with him anyway. Later Ripley asks Clemens how he ended up being a prison doctor and if he
committed a crime because he also has a barcode on his skin like the inmates. Clemens dodges the
question and in return asks about the real reason for the autopsy. To distract him, Ripley flirts
with him and they end up doing the dirty. In the meantime, Murphy is working in an isolated tunnel
when he finds a shed skin. Suddenly he hears a noise and thinks it’s Spike, but when he takes
a closer look he’s shocked to see the alien. The creature attacks by throwing acid at his face,
causing Murphy to stumble back and fall into a gigantic fan that immediately destroys him.
Soon Clemens is called to investigate Murphy's remains. Andrews thinks Murphy was distracted and
came too close to the sucking fan, but Clemens concludes that the fan was blowing in Murphy's
direction. He also finds a burn mark like the one Ripley saw on the hypersleep pod. Wanting answers,
Clemens goes looking for Ripley and finds her searching the ship wreckage for the
flight recorder. When he tells her about Murphy, Ripley begins to suspect there’s an alien around
and Clemens demands to hear the whole story, but before sharing that information Ripley wants to
recover the remains of the android. Clemens tells her to go to the garbage dump, but he can’t escort
her because he has a meeting with Andrews. When Clemens meets with Andrews, he immediately gets
scolded for letting Ripley wander alone. He also shares that they’ve received high-level
communication from the company regarding Ripley, who apparently is extremely important for the
higher-ups but Andrews doesn’t know why. An argument ensues on how to proceed and Andrews
tells Clemens to behave or he’ll tell Ripley about his dark past. Meanwhile Boggs, Rains, and Golic
are on a survey assignment that has them placing candles to measure various tunnels and rooms in
the building, however some candles in the distance keep getting blown out. Assuming it’s the wind,
Rains goes to re-light them only to find the now fully grown alien, which grabs Rains and begins
biting him. Boggs and Golic hear screaming and run to check on their friend, but as soon as they
see the creature they run back to the entrance. There they find Rains' dead body. Suddenly Boggs
is attacked from above by the alien, which rips out his throat. The blood sprays on Golic, who
after a moment of frozen shock runs away in panic. Back to Ripley, she searches the garbage dump and
finds the remains of the android. When she tries to leave she’s cornered by three prisoners, who
quickly jump on her and bend her over, intending to take advantage of her. At that moment Dillon
comes in and beats the inmates up with a piece of steel, threatening to reeducate them. Before
leaving, Ripley punches one of her attackers in the face. Afterward, Ripley connects what's left
of the android to a power supply in the infirmary and reactivates him. Using the android’s system,
she accesses the ship’s flight recorder and learns that a fire caused their ejection from the ship
and an alien traveled with them when they escaped the planet. This information has been shared with
the network, so the company knows about it. The android is in great pain and asks for mercy,
so Ripley permanently disconnects him. At that moment, Golic is dragged into the infirmary as
he swears that he didn’t kill anyone, a dragon did. Andrews and the others dismiss him as insane,
but Dillon defends him, saying that Golic has never been a liar. Ripley overhears everything
and comes out to confirm the story, but Andrews is still skeptical. They end up having a meeting in
his office and Ripley shares everything she knows about the aliens. Unfortunately Andrews reveals
that aside from some knives and fire axes, there are no weapons in the prison. He also confines
her to the infirmary until the rescue ship arrives, still not believing her story. Later
in the infirmary, Ripley isn’t feeling well and Clemens gives her another injection. Golic hears
her and says she’ll also die soon. To distract her, Clemens finally admits that he used to be a
prisoner too, sentenced after a medicine addiction caused him to take a bad medical decision and
several deaths. When the prison was turned into a lead shielding factory and the population reduced,
he decided to stay with the inmates, knowing no one else would hire him as a doctor ever again.
Suddenly a shadow appears behind the curtain and the alien reveals itself, killing Clemens
in seconds. Then it approaches Ripley and corners her against a wall, but after taking a close look,
the alien steps back and leaves through the ceiling, taking Clemens’ body with it. Ripley
rushes to the mess hall, where Andrews is trying to form a search party for Boggs and Rains. She
tells them the alien is here and Andrews doesn’t believe her, but when he tries to shut her up,
he’s snatched from above by the alien, leaving the vent dripping with blood afterwards. After
some initial panic, the prisoners gather in the assembly area and argue over who should take over
as a leader. Ripley interrupts them to tell them what she knows about the aliens, although this one
moves a little differently. The lack of weapons or a surveillance system makes planning difficult and
Morse gets furious, blaming Ripley for bringing the alien to the prison. Dillon shuts him up and
the group agrees to hear her out. Ripley asks for a floor plan and notices a large system of tunnels
plus a toxic waste containment unit that can be completely sealed off. There are also barrels of
highly combustible material behind a thick steel door. They decide to use that material to burn the
alien out of the tunnels and force it into the containment unit to trap it indefinitely. Soon
the inmates start making preparations by mopping the tunnel with the fuel. They also search for
working batteries for the flashlight that will give the signal. Smoking is forbidden because even
a small spark can trigger an explosion. While they work in the tunnels, they find areas with holes
caused by the alien’s acid. One of the inmates is taking a ladder and accidentally drops his flare,
but he retrieves it before it can cause an accident. Unfortunately this distraction
gives the alien the chance to attack him by surprise. The flare falls and ignites the fuel,
causing a huge explosion that starts a fire and kills various prisoners. Some men try to run away
but the flames get on them anyway and burn them down. Ripley and Dillon save as many people as
they can and eventually someone manages to start the sprinklers, but although the fire is gone now,
the group is severely smaller. Afterward the survivors move through the tunnels to
collect the bodies. While the prisoners argue over what to do, Ripley begins feeling unwell,
so she goes back to the wrecked ship to use the biomedical scanner. Aaron helps her handle the
machine and after a quick scan, they’re shocked to discover Ripley was impregnated by the alien. This
explains why the alien didn’t attack her, it’s protecting its offspring. Then Ripley asks Aaron
to send a message to the company, stating that the whole base has gone toxic and they should
stay away. Aaron is confused because the rescue ship is their only hope, so Ripley explains that
the company will take the alien to Earth to make weapons. When Aaron refuses to send the message,
Ripley furiously shakes him, but she doesn’t change his mind and decides to leave to search for
the alien. At that moment Aaron receives a message from the rescue ship saying they’ll arrive in two
hours and that the highest priority is to keep Ripley quarantined. With a flashlight in hand,
Ripley looks for the alien through dark corridors, following any strange noises. When she finally
sees the creature, she attacks it with a rod, only to discover she mistook a rusty pipe for
the alien's head and the noise came from the bugs inside. Suddenly the alien appears right
behind Ripley. Moments later, Dillon is startled by a presence, but it’s just Ripley. She explains
she searched for the alien and didn’t attack her because of her pregnancy, she also realizes that
the shape she saw on the scan is a Queen, meaning her alien baby can make thousands more. Ripley
asks Dillon to end things for her since she won’t survive the birth anyway, so Dillon gets ready to
kill her. However at the last second he changes his mind and points out that Ripley’s immunity
can be used to their advantage. Ripley agrees to fight but makes Dillon promise he’ll end things
after they defeat the alien. Afterward Dillon gathers the inmates and Ripley explains the
company thought her old crew and even marines were expendable, so the chance they’ll let criminals
live is zero. Everyone agrees to fight and come up with a plan: some men will serve as bait and
guide the alien to the corridors of the lead works, closing off all the entrances until the
alien is forced into the mold. While everyone gets the doors and switches ready, Aaron sneaks away.
Dillon explains to Ripley the structure is old and hasn’t been used for five years, so some parts may
not work. This means they only have one chance to do this right. Morse tries to close the last door
but it isn’t working, and soon the alien attacks an inmate to kill him. Another prisoner sees this
and gets the creature’s attention to trigger the chase. As they run through the corridors,
the others close the doors to force the alien into the right path. However the maze-like design of
the area confuses everyone and they aren’t sure what doors to close anymore, not to mention the
alien breaking the window of one of them. After they lose track of the creature, an inmate goes
looking for it and gets its attention again with a flare. The chase restarts and although they keep
on closing doors, two more guys get killed. A guy panics and almost activates the piston too soon,
but Ripley stops him just in time. Outside, the ship with the company workers finally lands and
Aaron receives them, telling them that Ripley is in the furnace area. The group makes their
way inside while carrying a huge steel cage. Then Dillon enters the tunnels and finds the
alien killing another prisoner, so he drags the body away from the creature’s clutches and drops
him near the mold as bait. The alien comes closer and a prisoner activates the piston, however the
alien realizes it’s a trap and drags the body back into the tunnels without stepping into
the mold. Now they have five minutes to bait the alien again before the piston shuts the mold off.
The team runs through the corridors in different directions, trying to find the alien. While Ripley
keeps on finding bodies, an inmate runs as fast as he can only for the alien to grab and kill him
before he can enter the mold. In another corridor, Morse bumps into a prisoner and they both fall.
While they laugh at the false scare, the alien uses the chance to kill the other man. Morse moves
away from the alien while Ripley arrives with a flare and starts struggling with the alien,
trying to force it to attack her. At that moment Dillon arrives and drags her away as she screams,
so the alien follows them to protect its offspring. This finally makes the creature
enter the mold and Morse closes the door to trap it. While Morse runs to the lead platform,
Ripley tries to stay in the mold too, but Dillon pulls her away and promises to kill her later. The
duo starts to climb out only to notice the alien is following them, so Dillon decides to stay in
the mold to keep the alien there. While the alien attacks Dillon, Ripley climbs out and tells Morse
to pour the hot lead into the mold, completely covering both the alien and Dillon. Thinking it’s
finally over, Morse celebrates, however the alien comes out of the mold and starts chasing after
Ripley. She starts climbing a series of chains, but the alien climbs after her at great speed. At
that moment Morse shouts to Ripley to remind her of the sprinkler system, so she jumps to activate
it. The water falls on the alien and the sudden cooling causes cracks all over its body until it
finally explodes. Then Ripley joins Morse on the platform, only to be suddenly surrounded by Aaron
and the company employees. To Ripley’s shock, she can see the same android from her last crew,
but this guy is actually human and the designer that gave the androids his face. He swears they’ll
destroy the fetus after removing it from Ripley’s body, but she doesn’t believe him and closes the
fence between the platform and the group. Morse tries to move away, but one of the guards soldiers
immediately shoots him in the leg. Seeing Ripley was right, Aaron hits the designer in the back
with a pipe, causing the soldiers to shoot him and kill him. Meanwhile Ripley asks Morse to help her
one last time, and he moves the platform over the boiling furnace. Determined to end it all,
Ripley falls off the platform. At that moment the alien bursts out of her chest,
but Ripley holds tightly onto it and they both die as soon as they land in the flames. In the end,
the scientists bandage Morse and take him with them. In the wreckage of the ship,
Ripley’s recording from her first adventure can be heard saying she’s the last survivor.