“Publishing these short essays about numerous investigations in which, thanks to the special talents of my friend, I had the opportunity to be involved as a listener, and then as an actor, I, quite naturally, dwelled on his successes, omitting his failures. And not so much for the sake of his reputation - his energy and resourcefulness acquired special strength when he was at a loss - but because where he failed, too often no one else succeeded, and the story remained forever unfinished. However, when he made a mistake, sometimes the truth was still revealed. I have notes on half a dozen mysteries of this kind, and among them the "Adventures with the Musgrave Ritual" and the one I intend to tell about now are of the greatest interest..."