“That’s right,” agreed Bailey morosely.

“There’ll be none, or too many, on the blotter, but try, Bailey, try,” said Alleyn. He wandered about the room, his eyes on the floor; got as far as the window and stopped.

“Fox!” he said. “A clue. A very palpable clue.”

“What is it?” asked Fox.

“The odd wisp of blotting-paper, no less.” Alleyn’s gaze traveled up the side of the window curtain. “Can I believe my eyes?”

He got a chair, stood on the seat, and with his gloved hand pulled the buttons from the ends of the curtain rod.

“Look at this.” He turned to the radio, detached the control knobs, and laid them beside the ones he had removed from the curtain rod.

Ten minutes later Inspector Fox knocked on the drawing-room door and was admitted by Guy Tonks. Phillipa had got the fire going and the family was gathered round it. They looked as though they had not moved or spoken to one another for a long time.

It was Phillipa who spoke first to Fox. “Do you want one of us?” she asked.

“If you please, miss,” said Fox. “Inspector Alleyn would like to see Mr. Guy Tonks for a moment, if convenient.”

“I’ll come,” said Guy, and led the way to the study. At the door he paused. “Is he—my father—still—?”

“No, no, sir,” said Fox comfortably. “It’s all ship-shape in there again.”

With a lift of his chin Guy opened the door and went in, followed by Fox. Alleyn was alone, seated at the desk. He rose to his feet.

“You want to speak to me?” asked Guy.

“Yes, if I may. This has all been a great shock to you, of course. Won’t you sit down?”

Guy sat in the chair farthest away from the radio.

“What killed my father? Was it a stroke?”

“The doctors are not quite certain. There will have to be a post-mortem. ”

“Good God! And an inquest?”

“I’m afraid so.”

“Horrible!” said Guy violently. “What do they think was the matter? Why the devil do these quacks have to be so mysterious? What killed him?”

“They think an electric shock.”

“How did it happen?”

“We don’t know. It looks as if he got it from the wireless.”

“Surely that’s impossible. I thought they were foolproof.”

“I believe they are, if left to themselves.”

For a second undoubtedly Guy was startled. Then a look of relief came into his eyes. He seemed to relax all over.

“Of course,” he said, “he was always monkeying about with it. What had he done?”

“Nothing.”

“But you said—if it killed him he must have done something to it.”

“If anyone interfered with the set it was put right afterwards.”

Guy’s lips parted but he did not speak. He had gone very white.

“So you see,” said Alleyn, “your father could not have done anything.”

“Then it was not the radio that killed him.”

“That we hope will be determined by the post-mortem. ”

“I don’t know anything about wireless,” said Guy suddenly. “I don’t understand. This doesn’t seem to make sense. Nobody ever touched the thing except my father. He was most particular about it. Nobody went near the wireless.”

“I see. He was an enthusiast?”

“Yes, it was his only enthusiasm except—except his business.”

“One of my men is a bit of an expert,” Alleyn said. “He says this is a remarkably good set. You are not an expert, you say. Is there anyone in the house who is?”

“My young brother was interested at one time. He’s given it up. My father wouldn’t allow another radio in the house.”

“Perhaps he may be able to suggest something.”

“But if the thing’s all right now—”

“We’ve got to explore every possibility.”

“You speak as if—as—if—”

“I speak as I am bound to speak before there has been an inquest,” said Alleyn. “Had anyone a grudge against your father, Mr. Tonks?”

Up went Guy’s chin again. He looked Alleyn squarely in the eyes.

“Almost everyone who knew him,” said Guy.

“Is that an exaggeration?”

“No. You think he was murdered, don’t you?”

Alleyn suddenly pointed to the desk beside him.

“Have you ever seen those before?” he asked abruptly. Guy stared at two black knobs that lay side by side on an ashtray.

“Those?” he said. “No. What are they?”

“I believe they are the agents of your father’s death.”

The study door opened and Arthur Tonks came in.

“Guy,” he said, “what’s happening? We can’t stay cooped up together all day. I can’t stand it. For God’s sake, what happened to him?”

“They think those things killed him,” said Guy.

“Those?” For a split second Arthur’s glance slewed to the curtain rods. Then, with a characteristic flicker of his eyelids, he looked away again.

“What do you mean?” he asked Alleyn.

“Will you try one of those knobs on the shaft of the volume control?”

“But,” said Arthur, “they’re metal.”

“It’s disconnected,” said Alleyn.

Arthur picked one of the knobs from the tray, turned to the radio, and fitted the knob over one of the exposed shafts.

“It’s too loose,” he said quickly, “it would fall off.”

“Not if it was packed—with blotting-paper, for instance.”

“Where did you find these things?” demanded Arthur.

“I think you recognized them, didn’t you? I saw you glance at the curtain rod.”

“Of course I recognized them. I did a portrait of Phillipa against those curtains when—he—was away last year. I’ve painted the damn things.”

“Look here,” interrupted Guy, “exactly what are you driving at, Mr. Alleyn? If you mean to suggest that my brother—”

“I!” cried Arthur. “What’s it got to do with me? Why should you suppose—”

“I found traces of blotting-paper on the shafts and inside the metal knobs,” said Alleyn. “It suggested a substitution of the metal knobs for the bakelite ones. It is remarkable, don’t you think, that they should so closely resemble one another? If you examine them, of course, you find they are not identical. Still, the difference is scarcely perceptible.”

Arthur did not answer this. He was still looking at the wireless.

“I’ve always wanted to have a look at this set,” he said surprisingly.

“You are free to do so now,” said Alleyn politely. “We have finished with it for the time being.”

“Look here,” said Arthur suddenly, “suppose metal knobs were substituted for bakelite ones, it couldn’t kill him. He wouldn’t get a shock at all. Both the controls are grounded.”

“Have you noticed those very small holes drilled through the panel?” asked Alleyn. “Should they be there, do you think?”

Arthur peered at the little steel shafts. “By God, he’s right, Guy,” he said. “That’s how it was done.”

“Inspector Fox,” said Alleyn, “tells me those holes could be used for conducting wires and that a lead could be taken from the—the transformer, is it?—to one of the knobs.”

“And the other connected to earth,” said Fox. “It’s a job for an expert. He could get three hundred volts or so that way.”

“That’s not good enough,” said Arthur quickly; “there wouldn’t be enough current to do any damage—only a few hundredths of an amp.”

“I’m not an expert,” said Alleyn, “but I’m sure you’re right. Why were the holes drilled then? Do you imagine someone wanted to play a practical joke on your father?”

“A practical joke? On him?” Arthur gave an unpleasant screech of laughter. “Do you hear that, Guy?”

“Shut up,” said Guy. “After all, he is dead.”

“It seems almost too good to be true, doesn’t it?”

“Don’t be a bloody fool, Arthur. Pull yourself together. Can’t you see what this means? They think he’s been murdered.”

“Murdered! They’re wrong. None of us had the nerve for that, Mr. Inspector. Look at me. My hands are so shaky they told me I’d never be able to paint. That dates from when I was a kid and he shut me up in the cellars for a night. Look at me. Look at Guy. He’s not so vulnerable, but he caved in like the rest of us. We were conditioned to surrender. Do you know—”