The insdm2.pk3 file you have requested: Maps Levels Missions / 1 vs 1 / I to J Titles / The Darkness - 523.98kb is not available. Perhaps try browsing all files for the game Quake III Arena and upload any files you want to share or are missing. This is the only information we could locate:
A small arena-style level offering fast paced action. Has a quad damage near the upper part of the level, and a dark foggy tunnel beneath the main arena. Good for two to four players.