In Killing Floor you play as a part of a special team to fight off legions of cloned zombies. Horzine Biotech released an endless amount of clones from the facility and citizens are drowning in this waves of human flesh. Local police are trying to fight them back, but there is no progress. British government decides to build up a special team of fighters to fight off numerous amount of enemies on their territory.

Every level in the game has a precise amount of waves according to your difficulty. With each wave, the number of zombies and types will change becoming more challenging to live through. By successfully winning the round and depending on your skills, game awards with cash that you can spend on new weapon and supplies. High variety of classes have added a different gaming style for every player. You can be a Gunslinger and use pistols, Commando that uses rifles or Support that uses shotguns. Every class has their advantages and perks that can be unlocked by levelling it up. As the final wave players must face a boss with a unique mechanic.