This mod will basically tell the HL story as if Freeman never shut the portals and the aliens got out of Black Mesa, and onto city streets across America and eventually the world (hence the title).
You play as Geoff Burns, a lawyer who lives in a quiet suburb with his wife and 12-year-old daughter. On his way home from work one night, he gets into a car accident and suffers massive head trauma which sends him into a coma for 2 weeks. The doctors tell his family that he may never wake up again.
But, as you can probably guess, he does (it wouldn't be that fun to play as a guy in a vegatative state). He awakes to find the hospital in ruins, with all the doctors/patients killed and hideous creatures roaming the streets.
And it goes from there...
Some screenshots...(these are from a small section of the first area, the hospital).