‘As I stood in the study a further idea occurred to me. I had thought of a use for a brooch that had dropped from my wife’s clothes. It had fallen just behind the chair she had been sitting in, and I thought if I placed it on the floor behind a chair in his room, it would suggest she had been murdered here. My eye fell on a chair with a low back, standing in front of a curtain, and I saw at once it would suit my purpose. I dropped the brooch behind it and it caught on the braid at the bottom of the curtain. There it was hidden from casual inspection by the chair, but I knew the police would not overlook it. I withdrew without disturbing anything or leaving traces, closed the window, and returned to the city. ‘Such was my plot, and, but for your cleverness, it would have succeeded. Is there any other point on which you are not clear?’ ‘Only one, I think,’ answered La Touche. ‘You were heard to telephone on the Monday from the Café at Charenton to your butler and chief clerk. They received their messages on the Tuesday from Calais. How did you manage that?’ ‘Easily. I never telephoned on Monday at all. I slipped a tiny wooden wedge into the instrument to prevent the hook rising when I lifted off the receiver. No call was therefore made on the exchange, though I went through the form of speaking. Any other point?’ ‘I do not think so,’ returned La Touche, who again could not but feel a kind of rueful admiration for this ingenious ruffian. ‘Your statement has been very complete.’ ‘It is not quite complete,’ M. Boirac resumed. ‘There are two more points of which I wish to speak. Read that.’ He took a letter from his pocket and handed it to La Touche. Both men leaned a little forward to look. As they did so there was a slight click and the light went out. What sounded like Boirac’s chair was heard falling. ‘Hold the door!’ yelled La Touche, springing to his feet and fumbling for his electric torch. Mallet leaped for the door, but, tripping over the chair, missed it. As La Touche flashed on his light they could see it closing. There was a low, mocking laugh. Then the door slammed and they heard the key turn in the lock. La Touche fired rapidly through the panels, but there was no sound from without. Then Mallet flung himself on the handle. But at his first touch it came off. The holes for the screws had been enlarged so that they had no hold. The door opened inwards, and presented to the imprisoned men a smooth, unbroken surface, with nothing on which to pull. To push it towards the hall was impossible, as it shut solidly against the frame. Their only hope seemed to split it, but as they gazed at its solid oak timbers this hope died. ‘The window,’ cried La Touche, and they swung round. The sashes opened readily, but outside were shutters of steel plate, closely fastened. Both men shoved and prised with all their might. But Boirac had done his work well. They were immovable.