November 13th, 2493. Location: Trench system Valles Marineris, Mars - 72 hours ago the orbital satellite lost any contact to the colony MRS1. Since then, everlasting dust storms prevent satellite based bio-scan of the region. First details indicate an enormous disaster.
The International Community of States reacts surprisingly rapidly and arranges a crisis committee, consisting of politicians, military forces and delegates from leading trade and industrie concerns. 30 minutes after the incident first measures were arranged: "SS Callisto", supply spaceship, being on the way to Jupiter hastily leaves its planned route. 48 hours later it reaches the orbit of Mars.
Although depth scanners of the ship penetrate and reach upper layers of the underground Mars station, weak energy- and bio-signals provide rather an unclarified picture. In spite of some security considerations of the military, crisis committee decides to involve civil escort security of the supply ship in the mission.
Gunship Apocalypse, armed only with minimal weapons breaks into the atmosphere and takes course towards underground tunnels of the colony. It's mission: evacuation of eventual survivors and investigation of the near circumstances.