“Why, that the Oatviles were Catholics, nay, were noted Recusants, right up to the time of the third William. That means, of course, that they harboured priests; and you could not harbour priests within this distance of London without having a priests’ hiding-hole. There was a man, his name escapes me at the moment, who made it his special business to go about constructing these hiding-holes. A priori, then, it is fairly certain that there must be some architectural secret about the old manor-house of the Oatviles. And perhaps in this case they ran to a secret passage.” “Reeves, my boy,” said Gordon, “you’ll have to keep this dark, or they’ll be putting up the rent of your rooms.” Reeves still seemed a little dissatisfied. “But surely, Carmichael, while we were about it we could have kept watch in the room itself, and seen where the hiding-place is, and who comes out of it.” “We could have tried. But tell me: how much of our conversation does this gentleman overhear? And whereabouts in your room could you have hidden with any safety? Honestly, I don’t believe he would have come out except while he knew that you and Gordon were busy watching the wrong side of the door.” “You’re assuming, of course, that he can’t have got in at the door by a duplicate key after Reeves and I went to bed?” “I am not assuming that, I know it. I took the liberty of putting a bit of that useful chewing-gum across the lock of the door, and it was still undisturbed in the morning. Whereas the chewing-gum which stretched between the chairs had been ploughed up in every direction.” “As it is, though, we’ve still got to find the entrance to the passage.” “As you say. I thought we might spend a happy morning looking for it. Let’s see, there is a piano in your rooms; do you play it?” “Very badly.” “That’s exactly what we want.” “How do you mean?” “Why, if you sit in your rooms playing the piano, the gentleman on the other side of the partition will probably assume that nothing much is happening. If you play it loudly, you will drown any little thumping noises we may happen to make. And if you play it very badly, the gentleman on the other side, if he is at all musical, will probably retreat to the utmost limits of his hiding-place.” “But look here,” said Gordon, “we’re not certain this man is the murderer. Is it quite humane——” “Oh, shut up,” said Mordaunt Reeves. “You’re right, Carmichael, as usual. What’s wrong with starting now?” Reeves, it must be confessed, did his part of the programme admirably. He even sang to his own accompaniment. When he got to “Land of Hope and Glory,” Gordon asked if he might not have cotton-wool in his ears. He also expressed a fear that all the other residents would come in asking Reeves to stop. But fortunately it was a time of day at which the residents are either in London on business, or going round the links like sensible men.