In the 1980s, a company known as Marlokov Industries competed with Black Mesa. The founder, Rubert Marlokov caught wind of the new Anti-mass Spectrometer that was under development. A team was sent out to obtain a copy of the plans before it could be completed. Seeing that this could make him incredibly rich, Marlokov put the plan into action and had it fully built. Following the events of Aperture's down fall with GLaDOS, Marlokov attempted to one up Aperture and create an A.I. that couldn't fail named KALEB. A mixture of bad decisions and worst case scenarios lead to KALEB becoming slightly corrupted yet still functional. Many scientists bickered back and forth over shutting him down and with that, shutting down the facility. You, a normal janitor is on his way to work on this day. The day that may possibly be your last, or just the birth of a new chapter in your life. The Anti-mass Spectrometer is put into action, unleashing the hordes of Xen upon the facility and its inhabitants. KALEB is also affected by this, attempting to stop the Xen horde from attacking him as well as everyone else. He takes notices of you as you struggle to survive and offers you a way out. Along your journey you will meet many interesting characters, many willing to help you. Though in a mad world, who is the hero and who is the villain? Who is the trusted and who is the untrusted? Only time will tell, so keep all close, you never know who will follow through and who just might snap.