Delta Particles is a single-player modification for Half-Life that introduces an entirely new campaign set within the Half-Life universe. In this game, you assume the role of Nick Farrell, a technical engineer stationed at the high-tech Delta Base—a cutting-edge research facility located in the Nevada desert. The story unfolds when a catastrophic resonance cascade at Black Mesa teleports extraterrestrial beings from the alien world of Xen to Earth, plunging the base into chaos.