Time had become a blur for Simon since his sister had vanished. He still didn't want to believe it was true, but the more time that passed without her contacting him, the more he had to accept it- she was gone, he had no idea if she was going to come back, and even with the Doctor's reassurance that she was stopped in time and would be waiting for him... he still missed her, worried for her, the emotions like a small but constant pain deep in the pit of his stomach.

He spent a lot of time wandering the castle, knowing he was neglecting his offer to help Dr. Beckett, but not really caring at this particular moment, in a haze of sadness.

So he had to stop and look twice when he saw what appear to be a suit of armor- no, a person wearing armor- walking around.