World War II is ongoing. Germany broadly uses Enigma rotor cipher machines. The breaking of the Enigma code gives the Allies an advantage in the war — but this is just one side of the coin because the Enigma code is based on chaos, a non-measurable force lurking beyond the boundaries of our world and eager to consume all its flesh. The code decryption would stop the chaos invasion into our world.
An "Agency" operates in a secret heavily-guarded Victorian mansion somewhere in London suburbs; it has been opposing the supernatural for centuries. To break the Enigma code, the Agency has gathered the world's best decrypters together. You are one of them. Your mission is to break the Enigma code as soon as possible while wandering inside the mansion with an ever-changing layout. At least, you tell others so. In fact, you might pursue completely different goals..