The add-on to F.E.A.R. directly begins where the original left. You and two of your teammates, Holiday and Jin, survived the explosion of the secret laboratory and you're now on your way back to base by helicopter assuming the day had been saved and Alma and Fettel would be dead. But as always, nothing seems as it is and suddenly Alma boards the helicopter and it crashes down. Separated from your teammates, you make your way to the extraction point not knowing what awaits you...
During your quest you encounter once again the Replica-Soldiers and some new mysterious enemies whose intentions aren't quite clear. To deal with all your foes, you've access to the weaponry known from the original game like the Shotgun or the Nailgun but there also a few new guns available like the Minigun.
On some levels you can find XPS-themed monitors, CPU cases and laptops manufactured by Dell, which might be an in-game advertising.
In the subway levels, several places have subway maps present, probably to increase the sense of realism in the game. However, these maps are actually parts of the real New York City Metro subway maps. This is most likely an easter egg, since the events of F.E.A.R. take place in a fictional and seemingly west-coast city.