Commander Patrick Ross embarks on a daring mission to Mars, leading his crew into the unknown. During their expedition, they collect soil samples that inadvertently contain an alien substance. This alien matter thaws upon their return journey due to temperature changes and causes a disturbing seven-minute blackout in communication with mission control. When the astronauts return to Earth, they are met with accolades and public celebration, but not everyone is pleased; the institutionalized Dr. Cromwell reacts with intense fear and panic right upon their return.
Meanwhile, Dr. Laura Baker has been working on a significant project: creating a clone named Eve, derived from alien DNA but modified to suppress its more aggressive traits. Her team conducts a series of experiments on Eve, intending to explore potential defenses against any future alien threats. However, they continuously face setbacks as Eve’s unique biology adapts to their every effort.
Upon arriving back on Earth, the astronauts receive instructions to avoid sexual activity for ten days, a guideline that Patrick brazenly disregards. Following a fundraiser, he engages in a threesome with sisters Marcy and Lucy. Strangely, during his intimate encounter with Lucy, he starts growing tentacles. Upon realizing this transformation, Lucy is horrified and attempts to escape as she pleads for him to stop, but Patrick ignores her distress as he reaches a climactic moment. The alien essence within both Marcy and Lucy propels them into rapid pregnancies, leading to a grotesque and violent birth of Patrick’s half-alien offspring.
To conceal his monstrous progeny, Patrick hides them on his father Senator Judson Ross' property. With each sexual encounter, Eve becomes increasingly agitated. The next day, Patrick confesses to his father that he has no memory of the previous night's events. Senator Ross, aware of his son's reckless behavior, advises him to concentrate on his political ambitions.
However, Dr. Orinsky, a NASA scientist analyzing Patrick's blood, uncovers unsettling anomalies and attempts to alert Cromwell, only to be ambushed and fatally attacked by a creature birthed from Patrick's blood. When Laura analyzes Orinsky’s injuries, she discovers that the DNA doesn’t match Eve's, leading her to suspect Patrick as the true source of the threat.
As the situation escalates, Laura and her colleague Press Lennox confront the astronauts and discover that the alien seed is spreading like wildfire among them. Unfortunately, they are unable to save Anne Sampas, who becomes pregnant by her husband, resulting in a swift and violent demise when a tentacled creature erupts from her body, killing him in the process.
In the midst of the chaos, Patrick’s actions become increasingly sinister, culminating in the tragic death of his girlfriend due to another hybrid pregnancy. Amidst his horror, Patrick attempts suicide with a shotgun, but the alien DNA resurrects him, banishing his human emotions and compelling him to reproduce at a terrifying pace, hiding his victims and children beneath his father's roof.
As the military gets involved, Laura grapples with the decision to activate Eve’s dormant alien DNA to track Patrick. This reaction makes Eve more volatile, heightening the stakes of the game. With mounting tension, they attempt to contain Patrick, but he becomes aware of Eve's presence, leading to chaotic clashes that threaten all involved.
A culmination of terror occurs when the team learns that the insights from Dennis—who remains uninfected due to his sickle-cell disease—are key to countering Patrick's rampage. As the military and the team pursue their objectives, Eve breaks free in search of Patrick, leading to a dramatic showdown revealing Patrick’s full alien form.
In a heart-stopping clash, Press and Dennis rally together to confront the threats posed by the now fully transformed Patrick. As the battle unfolds, Eve's fate hangs in the balance, ultimately revealing the shocking truth of her and Patrick's bond as the screen fades to black, leaving a lingering sense of dread about the future.
