“What tom-fool idea?”

“To stage a series of apparent attempts on his own life based on an idea of mistaken identity. He planted that idea in all your heads. He insisted on it. He shoved you in and rescued you and then went about shouting that Hart had tried to drown him. Evidently he’d some such plan in his head on the first night. Hart had written threatening letters and Compline followed up by writing himself a threatening message with a rather crude imitation of Hart’s handwriting. Once we’d proved Hart didn’t write the message on the Charter form it was obvious only Nicholas could have done so. Perhaps he chucked you that cape deliberately. Before the bathing incident he knew where you all were and no doubt he watched Hart set off alone down the drive. If the plan failed there wasn’t much harm done. Next, he staged his own flight over country that he knew damned well was impassable. If nobody had gone with him he’d have come back half-drowned in snow and told the tale. Next he rigged up his own booby-trap, choosing a moment when you were all changing in your rooms. He hadn’t bargained on Madame Lisse looking after him as he went down the passage. He was going to kick the door open and let the brass Buddha fall on the floor. But, knowing that she was watching, he had to go a bit further than was comfortable, and he mucked up the business. He chose the Buddha because he’d seen Hart handle it the night before. He chose the Maori mere for the same reason, but he smudged Hart’s prints when he used it. He himself wore gloves, of course.”

“But the wireless?” asked Chloris.

“Do you remember that Hart had complained bitterly of the wireless? That appears in Mandrake’s most useful and exhaustive notes. Compline knew Hart loathed radio. After the fiasco at the pond he shut himself up in the smoking-room, didn’t he, until he was turned out by William, who wanted to make his drawing? And discordant noises were heard? He was always at the radio? Yes; well, he was making himself very familiar with that wireless set. Do you remember the fishing-rod above the mantelpiece in the smoking-room?”

“Yes,” they said.

“Complete with fly and cast and green line?”

“Yes.”

“Well, when we came on the scene there was no fly and the line had been freshly cut. On the screw-hole on the volume control I found a number of almost invisible scratches, all radiating outwards. I also found some minute fragments of red and green feathers. The card on the rod tells us that the late Mr. St. J. Worthington Royal used that red-and-green fly when he caught his four-and-a-half-pounder. There were other marks on the double tuning control which, at its centre, was free of dust. In the jamb of the door into the library there was a hole which accommodated the drawing-pin Mandrake picked up in the sole of his shoe. You saw that William dropped one of his drawing-pins in the smoking-room. I fancy Nicholas found and used it. In Mrs. Compline’s hat I found two flies, one red-and-green, rather the worse for wear. The maid who looked after her swears there was only one, a yellow-and-black salmon fly, when she arrived. Who went straight to his mother’s room after the murder? Right,” said Alleyn, answering their startled glances. “Well, yesterday evening we experimented. We found that if we used a length of fishing-line with a fly attached but without a cast, we could hook the fly in the screw-hole of the volume control, pass the green line under the wave band and over the tuning-control axis, which served as a sort of smooth-running pulley, and fix the other end of the line to the library doorjamb with a drawing-pin. When you tweaked the line the hook pulled the volume control from Zero to fairly loud, the line playing over the tuning control, which we had set in such a way that the slight pull turned it to the station. As the hook in the screw-hole reached the bottom of the circuit, it fell out and the wireless was giving tongue.”

There was a long silence, broken at last by Mandrake. “But nobody could have fixed it,” said Mandrake.

“Only after William was dead. He would have seen it when he was tuning, wouldn’t he? But this is the place, I see, to introduce Thomas, the dancing footman. Thomas set a limit to the time when the murderer departed. Incidentally he also proved, by a little excursion, that Hart couldn’t have shoved you in the pond. Thomas was Nicholas Compline’s undoing. If it hadn’t been for Thomas we would have had a job proving that Hart didn’t do exactly what Nicholas said he did: creep in by the door from the hall into the smoking-room and kill William. The mistaken identity stunt had to be supported by an approach from the ‘boudoir.’ But as things stood it was perfectly clear from the start that only Nicholas could have benefited by the wireless alibi. Mr. Royal, whose trip into the hall looked rather fishy, left the library after the wireless started, and Dr. Hart would have gained nothing whatsoever by the trick since he was alone for the entire time. Lady Hersey, who had no motive, is the stock figure of thriller-fiction — the all-too-obvious suspect. Moreover the trout-line device would have been of no use to her, either, since she went in after the noise started.”

“What exactly did he do, though?” asked Chloris.

“He killed his brother, rigged the wireless trick, came out and shut the door. Later, he opened the door, held a one-sided conversation with William, asked for the news, tweaked the string which he had pinned to the door-jamb and waited, with God knows what sensations, for someone to go into the smoking-room.”

“What happened to the line?”

“You will remember, Mandrake, that while you and Mr. Royal were together by the body, Nicholas came in. He had shut the door after him and was hidden from you by the screen. He had only to stoop and pull the line towards him. The drawing-pin had jerked away and he had not time to hunt for it. The line was in heavy shadow and the same colour as the carpet. It throws back well towards the screen when the trick is worked. He gathered it up and put it on the fire when he got the chance. You left him by the fire for a moment, perhaps.”

“He asked us to leave him to himself.”

“I’ll be bound he did. But a trout-line doesn’t burn without leaving a trace and we found its trace in the ashes.”

“I see,” said Mandrake.

“I can’t help thinking about his mother,” said Chloris. “I mean, it was Nicholas she adored.”

“And for that reason she killed herself. At the inquest you will hear the letter she wrote. Mandrake has already seen it. She hoped to save Nicholas by that letter. While seeming to make a confession, it tells him that she knew what he had done. No wonder he was upset when he read it. It was her last gesture of love — a very terrible gesture.”

“I think,” said Chloris shakily, “that he truly was fond of her.”

“Perhaps,” said Alleyn.

The library door opened and Hersey’s face, very pale and exhausted, looked in. “Is it an official party?” she asked. Alleyn asked her to come in. “I have already been over a good deal of this with Lady Hersey and with Mr. Royal,” he explained, and to Hersey: “I have not got as far as your visit with Nicholas Compline to his mother.”

“Oh, yes. You asked me last night to tell you exactly what he did and I couldn’t remember very clearly. That’s why I’ve come in. I’ve remembered what happened after he’d tried to tell her about William. I’m afraid it’s quite insignificant. He seemed frightfully upset, of course, and I suppose in a ghastly sort of way he was. He didn’t make her understand and turned away. I had to tell her. I knelt by her bed and put my arms around her. We were old friends, you know. I told her as best I could. I remember, now, hearing him walk away behind me and I remember that in the back of my head I was irritated with him because he seemed to be fidgeting about by the wardrobe. He must have been in a pretty awful state of mind. He was swinging the wardrobe door, I thought. I suppose he didn’t know what he was doing.”