You wake up in the lower maintenance area of what you discover to be the SETO Station 50 Research Vessel A (50XA), a company-owned space station working on bioengineering sometime in the late 21st century.

You appear to have fallen down this far through an access shaft, though you cannot get back up this way. Making your way through the lower area, you find evidence that some sort of disease has killed off apparently the entire crew through various logs and diaries. Reaching the Upper maintenance level you learn of an accessible Escape Pod bay. Entering this area you at last come to the center of the game's action. A scientist has locked himself in an office by the pod bay, and he has the code to the last shuttle. He reveals that a number of survivors are locked in the Hospital Bay, though all sick and likely fading rapidly. You can hear him coughing terribly, and he tells you he has been infected by the disease. He will give you the code if you call for help as he can not make it to the Communications bay to fix the radio.

Arriving at Comms you find that the radio has been irreparably sabotaged, and suddenly you experience a major flashback that implies you may not actually be a member of the station's crew, but that you worked for someone else. As you arrive back at the pod bay, the man tells you that he cannot give you the code, as though you are clearly immune somehow to this disease, taking a shuttle of potentially infected air back to Earth could risk the whole planet. So, you must help him find a cure, using your blood as a starting point.

You head to the labs where a machine will take a sample. As the needle enters your skin you flashback again to getting a shot, revealing that you were carrying the engineered infection to the ship, and that you were given an immunity to it by the rival company you were a spy for.

You learn from the scientist that you must power up the labs in order for him to remotely use their instruments to synthesize a cure. You head to the power station to fix the lines to the lab, on the way finding a report filed by an anonymous science-crew member warning the administration on board that a spy was in their midst, and that he had an idea who it was. After restoring power to the labs (and as you find out, also restoring power to the Hospital Bay airlock controls) you flashback to the scientist confronting you, (accurately) accusing you of being the spy, pinning the (at the time) two original disease-related crew deaths on you as well as the dozen infected members. You, smugly, all but come completely clean, and he in a desperate rage pushes you down an open access shaft, where you fall and are knocked unconscious (thus the beginning the game).

At this point, the player decides the ending. Back in the bay, the player can either: A. give the scientist the blood sample, allowing him to make a cure, saving the survivors on board, and essentially marking a "rebirth" for the player, leaving his old self behind...or B. using the newly activated Hospital Bay airlock controls to threaten the Scientist to give you the code or else you will send the survivors into space. He does, and you "finish the job", ejecting them, then taking the shuttle to Earth, leaving the Scientist to die alone. Back home the rival company pays you well, and offers you a position heading their next project: infect the general populace with the same disease tested on 50XA, and sell the cure for profit.

Alternatively the player may also find, through a complicated puzzle, an extra copy of the escape shuttle code, and he can take it before giving the blood sample. This ends in a third conclusion, where the player leaves the survivors to die, and arriving home is payed handsomely by the rival company, but turns down their offer to lead their next project, saying he needs no more money and would rather fend for himself than pledge allegiance to the company.