“That is another line of thought. There are two, and I beg you will not tangle them. Line A, which concerns Lady Beatrice, has a vaguely sinister flavour, has it not?”

“I can make nothing of it.”

“Well, now, let us take up line B, which concerns Sir Robert. He is mad keen upon winning the Derby. He is in the hands of the Jews, and may at any moment be sold up and his racing stables seized by his creditors. He is a daring and desperate man. He derives his income from his sister. His sister’s maid is his willing tool. So far we seem to be on fairly safe ground, do we not?”

“But the crypt?”

“Ah, yes, the crypt! Let us suppose, Watson⁠—it is merely a scandalous supposition, a hypothesis put forward for argument’s sake⁠—that Sir Robert has done away with his sister.”

“My dear Holmes, it is out of the question.”