“Well, Mr Holmes, what do you make of that?” Inspector Lestrade asked. He seemed on edge, and well he might do, since we were looking at the body of the dean, sprawled before the altar, the blood-stained clothing showing all too clearly what had happened to him.

Holmes peered closely at the body and then said, “Was the dean in the habit of prostrating himself? I can see no signs of him being forced down and the angle of the wound would indicate a downward thrust.”

“He was,” Lestrade said. “It was a well-known fact.”

“Did he have many enemies? He was an ambitious man, so it seems likely.”

“From what I can gather, talking to the cathedral servants, his main enemy was the bishop. But surely you can’t think…”

“You know my methods, it would seem impossible for anyone to approach the dean without being noticed, and therefore, we have to accept the improbable, that the bishop was able to pass by the dean, for no-one would have looked too closely, and stabbed him.”

“But,” Lestrade protested, “someone would have noticed the bishop bending down to stab the dean.”

“I suggest we take a look at the bishop’s crook.”

Without another word, Holmes took off across the cathedral and Lestrade and I hurried after him. He burst into the bishop’s office, ignored the prelate’s objections, and took up his crozier. After running his hand around the upper part of the crook, he gave an exclamation and we saw a sharp stiletto shoot out of the end of the crook.

“And that is how it was done,” Holmes said triumphantly.