You are Gordon Freeman, formerly a scientist at Black Mesa Research Establishment, now reluctantly employed by a mysterious organisation as a troubleshooter. (They send you out looking for trouble, and when you find it, you shoot it.)
You are contacted by the Man in Blue. He seems strangely worried; something has ruffled his normally impenetrable character.
"Mr Freeman, we need your help urgently. It seems that somebody at Black Mesa has been experimenting with ... unconventional applications of the dimensional gateway technology. They have developed what appears to be a working time machine.
"Unfortunately, the scientists who were working on it disappeared before we could ... persuade them to turn it over to us. It appears that we were not the only ones following their work from behind the scenes. A renegade organisation within the US Marine Corps got to them before we did, and used their technology to travel into the past..
Gordon Freeman against Naziz.
Author: Ross Smith