You don't explain everything when you're writing. It's pretty damn clear. It even says he has amnesia in

The mess...just a pawn in a game of chess, assaulted by a bout of amnesia.

It says that he was remembering in

Who am I......" he cried, his brain expanding and his thoughts suddenly back,
remembering, daydreaming, or maybe just rolling over the grizzly, ghastly facts.

It seems pretty damn clear to me.