We've finished with the canonical Marathon Trilogy and are moving on to third party scenarios, starting with EVIL. In this scenario, a UESC ship from Tau Ceti runs into a spatial anomaly that sends them far away where we encounter something dark and evil.
A special task force awaits to help us take out a special Juggernaut. If only we weren't so impatient.
EVIL can be played, like the other Marathon games, using the open source Aleph One engine which you can get here for Windows, Mac and Linux: