A cemetery in the swamp near Arkham, July 1923: A man is his twenties is standing next to an open crypt, a horrified expression on his face. The meager light of his lantern reveals a set of stairs leading into the depths of a dark and foul-smelling crypt. Next to him are a backpack, a spade, and a portable telephone, with it cable leading down the stairs into the darkness. "Get out! Push back the grave slab and RUN!" cries a panicked voice through the receiver. "I can't leave you, Harley," he answers in a trembling voice. "Harley, can you hear me?", he screams. A cracking noise over the receiver makes him pause. Then a hollow, gelatinous, disembodied voice echoes through the receiver: "YOU FOOL, HARLEY IS DEAD." The man begins laughing hysterically. To protect his sanity, his heart stops and he drops down dead.

Forbidden Knowledge is a new case in the innovative game series Undo. As players travel through the dead man's past and try to give him a future, they gradually explore a horrifying story that is not from this earth.