An astronaut named Riya finds herself waking up abruptly aboard a desolate scientific research station on a remote planet, having no memory of her circumstances—where she is or how she arrived there. Her only recollections are fragmented, nightmarish images that haunt her as she begins to explore the eerie station. During her investigation, she discovers multiple corpses, intensifying the mystery surrounding her situation, until she hears an unexpected sound coming from the station's airlock. When she confronts this newcomer, she meets Brion, who insists that he knows her and claims to have responded to a distress signal sent out from her location.
As Riya and Brion begin to piece together the situation with the aid of sporadic flashbacks, it becomes clear that they were once part of a crew made up of several members, including Adhi (the commanding officer), Kevin (Riya's boyfriend), and others like Clarke and Davis. This crew was dedicated to various exploratory missions from Earth, aiming to identify new habitable worlds. With all prior expeditions having gone missing, the current planet, designated K.O.I.-442 and dubbed "Ash" by Kevin, represents humanity's last hope for success in finding a suitable home elsewhere. While the crew resided on the surface, Brion remained in orbit, tasked with maintaining contact with Earth and overseeing the crew's efforts.
After failing to locate Clarke, the only crew member not found among the deceased, Riya and Brion begin preparations to evacuate the planet within twelve hours, as the systems of the ground station are compromised and life support is dwindling. Riya soon experiences increasingly vivid flashbacks depicting her crew meeting alarming fates, some of which implicate her own involvement. Amidst an unforeseen meteor storm, alarms indicate a breach in the hull. While attempting to seal this breach, Riya uncovers evidence suggesting that someone has been navigating the maintenance shafts. This leads her to suspect that Clarke is still alive, possibly infected by a strange force that has driven her to madness, resulting in the crew's deaths and the station's current sabotage.
As oxygen levels drop dangerously low, Riya and Brion realize they must leave for the orbital facility to avoid suffocation. In a drone's collected recordings, Riya learns of Brion’s discovery of alien atmospheric converters that led to the death of Davis. She confronts Brion about his withholding of critical information, and in her fragmented memories, she acknowledges her role in the deaths of both Kevin and Adhi, although the reasoning remains elusive. Brion, prioritizing the groundbreaking discovery of advanced extraterrestrial life and terraforming, insists on continuing with their evacuation rather than delving into past trauma.
With limited time before Brion's lander initiates automatic takeoff, they both gear up for their escape. Just then, Riya suddenly recalls a harrowing moment in which Adhi attacked her, leading her to act in self-defense. However, while recovering from this traumatic memory, she encounters an unexpected presence in an EVA suit—Clarke. In a panic, Riya races into the maintenance tunnels, only to discover Brion dead. Confronted by Clarke's aggressiveness, Riya retreats to the bathroom, where in an intense moment, she uses a shower hose to drown Clarke, believing her to be infected. However, upon scanning Clarke's lifeless body, Riya finds no signs of infection. Compelled by the approaching launch of the orbital line-up and the sabotage of her escape craft, she returns to the station only to realize Brion's body reveals he had perished long before their meeting.
This shocking revelation leads Riya to understand that she is the one who has become infected, and Brion's presence was nothing more than an illusion created by a parasitic entity within her. The alien lifeform had inadvertently entered the station, brought by Kevin, and subsequently infiltrated the systems. Flashbacks reveal the crew's discord as Riya insisted on remaining at the station against their better judgment to uncover terraforming technology. Following a series of horrifying events, including Riya inadvertently killing her crew members, she attempts suicide to escape the parasite’s influence. Yet, she survives when the parasite neutralizes the poison she ingests.
Just as Riya believes she can regain control, the parasite declares that its kind has claimed the planet long before the arrival of humanity, deeming Earthlings an inefficient life form and choosing to integrate and evolve her. Resolute against submission, Riya manages to have the parasite removed. However, an unexpected turn occurs when it reanimates Brion's corpse to confront her. In a fierce struggle, Riya uses a welding torch to defeat the creature and escapes from the inferno of the station. As she restores the lander's systems, she sets off toward the orbital facility, only to discover that it, too, has been compromised by the insidious infestation.
