STORY:

You are Adrian Shepard,
in stasis since the debacle at Black Mesa. 
        But fortunate for you, a situation occurs where you come of use again.
and so the G-man comes back to bring you out of stasis.

The events in this game happen a bit before Gordon arrives in City 17,
the player will start in black mesa-ish base thats still resistent to the
combine occupation, from there it will bring the player to a quarry, 
a soviet submarine base and into the basements of a older
citadell where the combine stumbled on ancient alien technology.