Source plot synopsis — includes the ending
The commercial space tug Nostromo is returning to Earth with a seven-member crew in stasis: captain Dallas, executive officer Kane, warrant officer Ripley, navigator Lambert, science officer Ash, and engineers Parker and Brett, along with the ship's cat, Jones. The ship's computer, "Mother", detects a transmission from a nearby exomoon and wakes the crew. Following company policy to investigate transmissions indicating intelligent life, they leave their payload in orbit and land on the surface, but the ship is damaged. Dallas, Kane, and Lambert discover that the transmission comes from a derelict alien vessel. Inside is a giant, fossilized alien corpse with a hole in its torso. Meanwhile, Mother partially deciphers the transmission, which Ripley determines is a warning beacon and not an SOS as initially thought.
Kane enters a chamber containing hundreds of large eggs. When he touches one, an arthropod-like life form springs out, penetrates his helmet, and attaches to his face. Back at the Nostromo, Ripley refuses to allow them aboard, citing quarantine regulations, but Ash disobeys her. While the engineers work on ship repairs, Ash attempts to extricate the creature from Kane's face but stops when he discovers that its highly corrosive acidic blood could harm Kane and damage the ship's hull. The creature eventually detaches itself and dies. After the crew returns to space, Kane awakens and seems well. During a final crew meal before returning to stasis, he suddenly chokes and convulses as a small alien creature bursts from his chest and escapes into the ship.
After ejecting Kane's body into space, the crew uses tracking devices to try to locate and kill the creature. Encountering Jones, Brett follows him into a landing leg compartment, where the now fully-grown alien kills him. The crew determines that the alien is moving around the ship within the air ducts, and Dallas devises a plan to force the creature off the ship with an airlock. Dallas asks Mother about alternative methods of killing the alien and their chances of succeeding, but the computer refuses to answer. He then enters the ducts with a flamethrower but is ambushed and killed by the alien.
A panic-stricken Lambert suggests abandoning the Nostromo and leaving in the ship's escape shuttle. Ripley, now in command, rejects the plan because the shuttle cannot support the remaining four crew members and decides that they will reattempt Dallas's plan. She accesses Mother herself and discovers a secret company directive: Ash must return with the alien for study, regardless of risk to the crew. Ash attempts to kill her when confronted, but Parker arrives and incapacitates Ash, who is revealed to be an android. Upon interrogation, Ash admires the alien and claims that the crew stands no chance against it. Parker incinerates Ash's remains.
Hearing this, Ripley decides to proceed with Lambert's plan and initiate the Nostromo's self-destruct mechanism. While they are gathering supplies, the alien kills Parker and Lambert. Now alone, Ripley begins the self-destruction, but the alien blocks her route to the escape shuttle. She narrowly escapes and turns back to abort the sequence but fails to return before the override option expires. With only five minutes left to evacuate, Ripley frantically returns to the shuttle and finds that the alien is gone. She takes Jones, boards the shuttle and launches it seconds before the Nostromo explodes.
As Ripley prepares for stasis, she discovers that the alien has stowed itself in a narrow compartment aboard the shuttle. She dons a spacesuit, loads a grappling hook gun, and straps herself to a chair before discharging gases to drive the alien from its hiding place. It tries to attack her, but she opens the shuttle door. The resulting depressurization blast leaves the alien clinging to the door frame. Ripley shoots it with the gun, knocking it out, but the door closes on the grapple line, leaving the alien tethered to the ship. She then fires the engines to sever the line and blast the alien into space. After recording her log entry, she places Jones and herself into stasis to start their return journey to Earth.
Kane enters a chamber containing hundreds of large eggs. When he touches one, an arthropod-like life form springs out, penetrates his helmet, and attaches to his face. Back at the Nostromo, Ripley refuses to allow them aboard, citing quarantine regulations, but Ash disobeys her. While the engineers work on ship repairs, Ash attempts to extricate the creature from Kane's face but stops when he discovers that its highly corrosive acidic blood could harm Kane and damage the ship's hull. The creature eventually detaches itself and dies. After the crew returns to space, Kane awakens and seems well. During a final crew meal before returning to stasis, he suddenly chokes and convulses as a small alien creature bursts from his chest and escapes into the ship.
After ejecting Kane's body into space, the crew uses tracking devices to try to locate and kill the creature. Encountering Jones, Brett follows him into a landing leg compartment, where the now fully-grown alien kills him. The crew determines that the alien is moving around the ship within the air ducts, and Dallas devises a plan to force the creature off the ship with an airlock. Dallas asks Mother about alternative methods of killing the alien and their chances of succeeding, but the computer refuses to answer. He then enters the ducts with a flamethrower but is ambushed and killed by the alien.
A panic-stricken Lambert suggests abandoning the Nostromo and leaving in the ship's escape shuttle. Ripley, now in command, rejects the plan because the shuttle cannot support the remaining four crew members and decides that they will reattempt Dallas's plan. She accesses Mother herself and discovers a secret company directive: Ash must return with the alien for study, regardless of risk to the crew. Ash attempts to kill her when confronted, but Parker arrives and incapacitates Ash, who is revealed to be an android. Upon interrogation, Ash admires the alien and claims that the crew stands no chance against it. Parker incinerates Ash's remains.
Hearing this, Ripley decides to proceed with Lambert's plan and initiate the Nostromo's self-destruct mechanism. While they are gathering supplies, the alien kills Parker and Lambert. Now alone, Ripley begins the self-destruction, but the alien blocks her route to the escape shuttle. She narrowly escapes and turns back to abort the sequence but fails to return before the override option expires. With only five minutes left to evacuate, Ripley frantically returns to the shuttle and finds that the alien is gone. She takes Jones, boards the shuttle and launches it seconds before the Nostromo explodes.
As Ripley prepares for stasis, she discovers that the alien has stowed itself in a narrow compartment aboard the shuttle. She dons a spacesuit, loads a grappling hook gun, and straps herself to a chair before discharging gases to drive the alien from its hiding place. It tries to attack her, but she opens the shuttle door. The resulting depressurization blast leaves the alien clinging to the door frame. Ripley shoots it with the gun, knocking it out, but the door closes on the grapple line, leaving the alien tethered to the ship. She then fires the engines to sever the line and blast the alien into space. After recording her log entry, she places Jones and herself into stasis to start their return journey to Earth.
Sources and content license
Source and revision history ↗ · Adapted from Wikipedia contributors, Alien (film). Section headings and formatting adjusted. · Content license