CIA has gathered some valuable intel on top-secret Soviet research outpost developing new chemical weapons that could have devastating effect on NATO invasion of Nogova .
Player, alongside his 3 highly SpecOps comrades, has been ordered to move in via chopper insertion into the Soviet outpost.
The first part of the mission would be classical clean-sweep and place a few satchel charges 'n' blow stuff up kind of mission, whilst on the second part, featuring the extraction things would get interesting. Player would board the chopper, which would, en route to NATO base would mysteriously loose control and crash near Soviet research outpost. This is when zombies make their first appearance. It turns out that chemical that Soviets were making, designed as terror weapon, reanimates dead tissue of humans, but also "deletes" any consciousness that previously inhabited the body. Turning humans back to animalistic instincts as well as making them more aggressive. Player has to find his way out of the Soviet compound and back to the NATO base, surviving on ever decreasing quantity of ammo and ever increasing number of zombies.
I suggest, if you are going to follow this idea, that you use Agent Smith's addons to make Soviet research compound.
Hope that helps,