“What would you do then?”

“Oh, you must not let me influence you in any way. I suggest that you go on your line and I on mine. We can compare notes afterwards, and each will supplement the other.”

“Very good,” said Lestrade.

“If you are going back to Pitt Street, you might see Mr. Horace Harker. Tell him for me that I have quite made up my mind, and that it is certain that a dangerous homicidal lunatic, with Napoleonic delusions, was in his house last night. It will be useful for his article.”

Lestrade stared.

“You don’t seriously believe that?”

Holmes smiled.