An 18 level solo scenario (plus 10 netmaps) that's been 4 years in the making. An answer to map-driven stories... this is a story-driven map. If you fell in love with Marathon because of its storyline, you owe it to yourself to play this one.
In the author's words, "this is a side trip in the Tempus Irae universe, and may be assumed to take place at any reasonable point during the original storyline."