Dark*Matter is a Horror/Sci-Fi campaign setting for the Alternity rules system created by TSR. The basic idea is "what if various conspiracy theories about aliens seeking to control earth, government coverups, magic, psionics and other strangeness were all real?" In this, it is a spiritual successor to Bureau 13. It should not be confused with Dark Conspiracy. It does share similarities in tome and feel to Delta Green, revolving as it does around the players taking the role of agents for the (supposedly) benevolent secret organization "The Hoffman Institute", and charged thereby with delving into the supernatural and mysterious - and keeping humanity ignorant of just what's out there in the dark.
It had a d20 Modern update in 2006.
- https://en.wikipedia.org/wiki/Dark%E2%80%A2Matter - Wikipedia's page on the game.
- https://projects.inklesspen.com/fatal-and-friends/freaking-crumbum/darkmatter/ - A /tg/ anon reads the corebook and dissects it.