The alien creature is a parasitic entity that originally inhabited the planet Ash. It manipulates the minds of the crew members, taking control and causing them to attack each other. The parasite eventually lodges itself inside the protagonist Riya's skull, manipulating her perceptions and making her see manifestations such as Brian, who is actually a part of the parasite's influence rather than a real person.

Clarke is the only crew member not initially found among the dead. Riya suspects Clarke is still alive and infected by an unknown entity that caused her to become psychotic, making her responsible for the crew's deaths and the sabotage of the station.

Riya and Brion are part of the exploratory expedition crew; Riya wakes up on the planet's station while Brion stayed on the orbital station to maintain contact with Earth. Brion arrives at the ground station after receiving Riya's distress call, and together they investigate the crew's massacre and try to survive.

The crew members, including Adhi, Kevin, Clarke, and Davis, were found dead under horrific circumstances. Riya experiences flashbacks suggesting she may have killed some of them, but it is later suspected that Clarke, infected and psychotic, was responsible for the murders and sabotage.

They face a failing life support system and a hull breach caused by sabotage. They have only twelve hours to reach the orbital station before oxygen runs out, all while dealing with paranoia, amnesia, and the threat of Clarke's possible presence.