“I had a very extraordinary experience once,” said Carmichael, “in Albania. I had to translate the confession of a dying man into French for the sake of a priest who didn’t know the local language. The priest told me afterwards I was bound not to disclose to anybody what I’d heard.” “He didn’t know you, anyhow, Carmichael,” suggested Reeves. “As a matter of fact, I’ve never mentioned what he said to anybody, though it was sufficiently curious.” “It’s impossible,” resumed Reeves, “not to make inferences; the mistake is to depend on them. In ordinary life, you have to take risks; you have to sit down in the barber’s chair, although you know it is just as easy for him to cut your throat as to shave you. But in detection one should take no chances, give no one the benefit of the doubt. Half of the undetected crimes in the world are due to our reluctance to suspect anybody.” “But surely,” urged Marryatt, “you would allow character to go for something? I was a schoolmaster once, and while one knew the little beasts were capable of almost anything, one did clear some people of suspicion on mere character.” “But there again,” argued Gordon, “you knew them very well.” “Not really,” said Marryatt. “A perpetual war of mutual deception is kept up between schoolmasters and schoolboys. One trusted, I think, one’s unconscious impressions most.” “If I were a detective,” persisted Reeves, “I would suspect my own father or mother as soon as anybody else. I would follow up every clue, blinding myself deliberately to the thought, where does this point to?” “Then you would be unreasonable,” said Gordon. “In the old days, when the answers of sums used always to come out to an integral number—I believe it’s all different now—one was wiser than that. If you could see that the answer was going to involve two-thirds of a policeman, you argued at once that you were on the wrong track; you started again, and suspected your working.” “But real life,” retorted Reeves, “doesn’t always work out to a simple answer. And if the policeman who’s in charge of a case argues as you’re arguing, he’s only himself to blame for it if he gets trisected by the criminal before he’s finished.” “At least you must respect the principle of _Cui bono_?” “It’s extraordinary,” began Carmichael, “how many people make the old mistake about the meaning of——” “_Cui bono_ is the worst offender of the lot,” said Mordaunt Reeves cheerfully. “Look at those two boys in America who murdered another boy just to find out what it felt like.” “But that was pathological.” “And how many crimes aren’t pathological, if it comes to that?” “I was on Holy Island once for a month,” said Carmichael, “and would you believe it, there was a man there that was sick if he ever caught sight of a dog? Sick, positively.”