In the original Todesangst we learn about Dr. Jack Newell and his horrifyingly successful endeavors to merge Xen and human life. Freeman and Joe, a courageous member of the Black Mesa security force, hunt down Dr. Newell and eventually succeed in smashing his biological engineering plots. The scheming doctor ironically meets his doom via his own creation, the "molecular transmutator" transforming him into a vicious Xenantromorph. Fade to black - roll the credits - end of story . . .or so we thought! Dr. Newell was the genius mind behind the experimentation and development of the Xenanthromorph program but the true power behind the clandestine research was a multi-national anarchistic group called Schwarzgeist. The Schwarzgeist had managed to put their personnel in key scientific positions within Black Mesa since its contruction. They managed to keep their identity secret until an inadvertent exposure during the resonance cascade disaster and ensuing containment revealed their...
In the early ages of this mod, this was amazing for standards provided by the early hammer editor. It came with it's own stunning soundtrack, a story to hallmark, level design that was worthy of Valve themselves and left a legacy of awesome HL1 mods in its wake.
I am glad I played this when I was in the early ages of my childhood.