Where does one stand in a world that's falling apart? Do you fight for your own survival... or for the greater good? When your race is going towards extinction, choices... just aren't as simple any more.
You are a mercenary for a subsidiary called "Ultimate Defense Contractors" (UDC), or simply known as Ultimate. Not long after your last mission, the CEO announced that a top secret contract had gone up and that it needed to be acted upon immediately. Before you know it, you're on a UDC spec ops helicopter on your way to the hot zone. You are not told where you are going. You are simply told to eliminate all hostiles in the area.
Although, something must be wrong here because you are required to wear a gas mask. You are told that there is a chemical agent in the air that can affect your neural system. You are also told that symptoms include paranoia, irritability, hallucinations and that it may be lethal.
Despite what they say, a glaring coincidence keeps bugging you: Medeiga Technologies, Ultimate's parent company, is in the weapons industry. Is this one of their products? Of course, you're not paid to think. As your air ride lands, fighting is the only option. Good luck.
The campaign starts with you being dropped off and takes you through the whole story behind the cause of the outbreak and how it changed the world.
Several days after the fight with the undead, the CEO specifically calls for you about another contract. What's funny is you're told the same exact things as with the previous mission. You immediately catch this and demand to know what exactly is going on. UDC blackmails you by telling you that you are infected with the Compound and that if you do not comply they won't give you the serum. You will become those things that you fought not too long ago. Not knowing whether it was a bluff or not, you couldn't take the chance. Even so, they could have easily gotten rid of you where you stand. Not knowing what else to do, you board another spec ops heli to an unknown destination. You'll find out that this destination is even worse than the first.
News channels around the globe report that the world is officially coming to an end. You tire of fighting the undead now. You're sick of them. After so much gore and combat, shacking yourself up in a bunker doesn't seem like such a bad idea. UDC still hasn't owned up on giving this serum they've been talking about. You start to question if you're even infected. There is a global fighting group called Ultimate Zombie Fighters (UZF). Maybe they'd be more help to you than your current company?
Nations have fallen. Civilization... what civilization? As part of UZF, you realize that the only hope your kind has is to go after UDC. To find the answers is to survive. You soon find out that UDC was being played by Medeiga. There was no serum to begin with. They were only blackmailing you because Medeiga was blackmailing them. With this brought to light, the UZF commander gives the CEO of Ultimate a deal: make Medeiga give them the serum or let their race go extinct. Obviously, the CEO joined forces. UZF had now gained a large amount of fighting power. With the many combat experts of UDC, UZF launches a campaign against Medeiga. So begins the war for survival.