Two centuries after the harrowing events of Alien 3, a daring team of military scientists aboard the USM Auriga embarks on an audacious experiment. They successfully create a clone of Ellen Ripley, known as Ripley 8, by merging her DNA with that of the Xenomorph queen. This genetic fusion results in a being possessing enhanced physical capabilities, acidic blood, and a unique psychic connection to the very creatures from which it originated. Moreover, Ripley 8 inherits fragmented memories of the original Ripley, making her a complex and formidable entity.

Concurrently, a group of mercenaries—comprising Elgyn, Johner, Christie, Vriess, Hillard, and Call—arrive at the Auriga aboard their ship, the Betty. Their mission involves delivering several captured humans in stasis, completely unaware that these unfortunate souls have been used as hosts for breeding Xenomorphs. Consequently, the mercenaries are unprepared for the onslaught of adult Aliens raised aboard the ship for study.

Their encounter with Ripley 8 proves significant, as she has evolved into a powerful and resolute figure. When Annalee Call recognizes her name, a sense of urgency drives her to eliminate Ripley 8, fearing she might be utilized to produce more Xenomorphs. However, the cloning has already occurred, and it’s too late to avert the impending disaster.

The mature Aliens break free from their confinement by killing one of their own, using its acidic blood to burn through their enclosures and capture Dr. Jonathan Gediman. This horrifying turn of events results in the deaths of most of the crew who did not manage to evacuate, including General Perez and Elgyn. As the ship spirals toward catastrophe, Dr. Wren reveals that the emergency protocol will return them to Earth, thus unleashing the Xenomorphs upon humanity.

Faced with this grim reality, Ripley 8, the mercenaries, Wren, soldier DiStephano, and the surviving host Purvis resolve to make their way to the Betty, intending to use it to destroy the Auriga. During their treacherous journey, Ripley 8 stumbles upon a laboratory showcasing the gruesome results of seven prior, failed attempts to clone Ellen Ripley. One desperate survivor pleads for euthanasia; moved by compassion, Ripley 8 complies and incinerates the lab in an act of fiery destruction and liberation.

As they navigate the ravaged vessel, peril awaits them at every turn. Their journey through a flooded kitchen is fraught with danger as they are pursued by two deadly Xenomorphs. In the ensuing chaos, one creature falls victim to Christie’s selfless sacrifice, while Hillard is violently snatched away by another Xenomorph. Escaping the kitchen, the remaining group members barely evade a still-pursuing Xenomorph, which blinds Christie in a moment of brutal violence.

The treachery of Wren sets a sinister tone as Call’s true nature is unveiled—she is an android, designed to interface with the ship’s systems. Leveraging her unique capabilities, Call initiates a collision course for the Auriga with Earth, aiming to eradicate the Xenomorph threat in a catastrophic crash. With Wren trapped and the Xenomorphs redirected toward him, Ripley 8 finds herself captured by one of the creatures as her companions advance toward the Betty.

In a desperate attempt to thwart Call’s deadly plot, Wren takes Purvis hostage, demanding she cancel the collision. However, an injured Purvis exacts his revenge on Wren, only for the Xenomorph embryo he carries to burst forth, claiming both their lives in the chaos. The remaining survivors manage to eliminate the juvenile Xenomorph and regroup with renewed determination to escape the doomed ship.

Meanwhile, Ripley 8 is drawn into the Alien nest, where she discovers Gediman, miraculously alive yet partially cocooned. The Alien queen, having formed a uterus due to genetic contamination with Ripley 8, gives birth to a Xenomorph hybrid portraying distinctly human traits. Unable to bond with its mother, the hybrid instinctively recognizes Ripley 8 as its true parent and embarks on a violent mission to kill the Alien queen and Gediman in an explosive display of maternal instinct.

Seizing the chaos as an opportunity for escape, Ripley 8 fights her way back to the Betty. The newborn hybrid, driven by an insatiable hunger for destruction, attacks Call, resulting in DiStephano’s tragic demise as he attempts to intervene. In a clever maneuver, Ripley 8 uses her acidic blood to create a diversion, allowing her to save Call and mislead the creature.

In a climactic act of defiance, Ripley 8 melts an opening into the ship’s hull with her acidic blood, pushing the hybrid toward the breach. The sudden decompression thrusts the creature into the void of space, where it meets its end, leaving Ripley 8 overwhelmed with a mixture of emotions.

As the countdown to the Auriga’s collision with Earth looms closer, Ripley 8, Call, Johner, and Vriess make their escape in the Betty. The ensuing explosion signifies the devastating impact of the ship with the planet, a testament to its catastrophic power. As they witness the destruction, Call turns to Ripley 8 and inquires about their future plans. With a hint of uncertainty, Ripley 8 reflects, “I don’t know. I’m a stranger here myself.”