"Doesn't remember? That's strange". Diamond thought about the evidence. None of it added up! It had seemed as though there was a reason for not killing Shae, and to have that reason, they'd have to know her, right? It wasn't like she was famous. But if this was the case, then how could no-one have any idea? The killing of all the servants who understood the signs couldn't be coincidental, could it? And if it indeed was not, then the perpetrator would have to know the servants, know exactly who each of them were to Shae, and so they would have to have been to the manor, after Shae's memory was lost, so why didn't she remember?
Clutching at any way to prove his theory, to not have to start back at square one, he rushed to Shae and inquired, "Were any of the birds harmed?" If they were, then the criminal would definitely have wanted to deliberately make Shae suffer. Well, maybe.