Suffering from amnesia you remember nothing of your past. Kaer Morhen, the last remaining keep of the witchers, was attacked by a mysterious organization, just as you were starting to lick your wounds there. The battle is won but the secret recipe for the mutagen, a substance required to create more of your kind, has been stolen. The surviving witchers set out to find and reclaim it and punish everyone involved. Memory loss or not, you are one of them.