“«It may cause him to be more cautious, or it may drive him to desperate measures at once. Like most clever criminals, he may be too confident in his own cleverness and imagine that he has completely deceived us.»
«Why should we not arrest him at once?» «My dear Watson, you were born to be a man of action. Your instinct is always to do something energetic.
But supposing, for argument's sake, that we had him arrested tonight, what on earth the better off should we be for that? We could prove nothing against him. There's the devilish cunning of it! If he were acting through a human agent we could get some evidence, but if we were to drag this great dog to the light of day it would not help us in putting a rope round the neck of its master.»”