Shadow remembers Wednesday telling him about the charms he knew. He remembers that Wednesday never would say what the eighteenth charm was, and he suspects it may have altered his memory.
Because when Shadow tries to remember how the night at Jack's ended, he finds he can't. And maybe it was the alcohol, but he thinks it might have been more than that.
He gets flashes sometimes, but they vanish like smoke when he tries to concentrate. Flashes of skin, and flesh on flesh, in the back of a sedan.
This much is true: the old man was a twisted bastard. Shadow wouldn't put anything past him. Not even that.