Set in the year 2794 A.D. the game places the player as a security officer; in actuality, he is most likely a Mjolnir Mark IV Cyborg, dispatched to respond to a distress signal sent from the enormous human starship called the U.E.S.C. Marathon, orbiting a colony on the planet Tau Ceti IV. Throughout the game, the player attempts to defend the ship (and its crew and colonists) from a race of alien slavers called the Pfhor. As he fights against the invaders, he witnesses interactions between the three shipboard AIs (Leela, Durandal and Tycho), and discovers that all is not as it seems aboard the Marathon. Among other problems, Durandal has gone rampant and appears to be playing the humans against the Pfhor to further his own mysterious agenda.