“It’s in connection with the death of Professor Arnell,” Cunningham began, and paused. Baker looked at him with an air of absolute astonishment that seemed too genuine to be “faked.” This man, Cunningham told himself, couldn’t possibly be the murderer. Or, if he was, he must also be a consummate actor in order to assume this appearance of complete surprise, not unmixed with consternation.

“Did I hear you say the death of Professor Arnell?” asked Baker.

Cunningham nodded. “Yes,” he said bluntly. “Professor Arnell died in London today.”

“Poor old chap!” exclaimed Baker. “Of course, I know that he’s had a groggy heart for years. Still, this will be a hell of a shock for Violet.” Then he paused suddenly, as if a new idea had suddenly come into his head. “But—I say, Sergeant,” he asked. “What are you doing here? I mean to say, there’s nothing fishy, nothing suspicious about the old man’s death, is there?”

“Only too suspicious, I’m afraid, sir,” answered Cunningham with a gloomy nod.

“You don’t say! Too bad! Poor old Violet will feel it terribly that her father has committed suicide.”

“Did I mention suicide, sir?” Cunningham asked quietly.

“No, now I come to think of it, you didn’t. But…but…you can’t mean,” asked Baker, his eyes opening widely, “you can’t mean—murder?”

“I’m afraid, sir,” Cunningham explained, “that we have only too sure grounds for suspecting that the professor was murdered. He died in the British Museum Reading Room. We have every reason for thinking that he was poisoned with a dose of cyanide.”

“Good God!” If Baker had been surprised before he was doubly astonished now. His face had gone white as a sheet, and now the blood was slowly flowing back into his countenance. Cunningham thought that this was too genuine to be assumed. Although, of course, he told himself, it was possible that the man had committed the murder, and had imagined that he was going to get away with it. It was possible that the sudden realisation that the police were on his track was sufficient shock to bring about this air of astonishment and horror. Anyhow, Cunningham had thought out his plan of campaign, and he was determined to follow it to the bitter end.

“I shall have to ask you a few questions, sir, as you will, of course, realise,” he said.

“Of course,” said Baker; “though what the devil you expect me to tell you about him I’m damned if I know. I wasn’t exactly a bosom pal of his, as I expect you’ve found out already.”

“We know that you were engaged to his daughter, sir,” Cunningham explained.

“And I expect you’ve also discovered that he didn’t precisely weep on the shoulder of his prospective son-in-law,” added Baker, with a somewhat sheepish grin.

“Yes; we’ve discovered that.”