There's something so remarkably feral about that laugh from Arthur, and the spread of his teeth. He's only ever seen the man like that when he's on the edge of his sanity thinking about things from... home. Puzzle pieces are falling into place. These two are speaking to each other like they know each other. Have history with each other. What really clinches it is that name. That name he's heard on Arthur's lips when he's talking to himself. Only, he was never just talking to himself.

I don't need you, John.

No. It can't be. Can it?

Horror-stricken, Crichton turns to look a that masked face, look into the eyes behind it, and his gun comes up and is now firmly trained on that sharply angled space between the eye holes.

"Arthur... Is this who I think it is? Is this the voice from your head?"