“Literary research work?” Shelley swiftly interrupted. “I never heard that Mr. Wallace was interested in any sort of literature.”

“Oh, he was exceedingly well read. He knew, especially, all about the lesser Elizabethan dramatists…” Henry’s voice slowly died away. A look of sudden comprehension came over his face. “Is that the connection with the death of Professor Arnell?” he asked in excited tones.

“It may be one connection,” Shelley admitted. “But a more or less accidental one, I imagine. Probably it was some such item of knowledge which suggested the way in which the murder was carried out.”

“Then he is the murderer?” Henry was really excited now.

“Yes.”

“But…but…I don’t see what he has to do with Professor Arnell,” complained Henry.

“Neither do I,” said Shelley. “I know how it was done. He probably knew Professor Arnell as a fellow-worker in the British Museum Library. He inserted the poisoned sweet in the packet which the Professor used to leave on his table in the library as he went to the central desk to hand in his tickets requesting books.”

“And Dr. Crocker?”

“He was enticed up from Oxford on a pledge of secrecy; probably by a forged note asking him to come to meet Professor Arnell, or, more likely, someone who could assist him to show up Professor Arnell as a fraud.”

“That’s possible. But what about Harry Baker?”

“Another decoy letter. Harry said that a letter had brought him there. You see, the decoy letter seems to be a favourite system of his. He used one—if what Moses Moss says is true—to get Moss away from Miss Arnell last evening so that he could bring off his little kidnapping trick.”

“But what on earth is the reason for all this?” asked Henry in astonishment.

“That’s what puzzles me, too,” Shelley admitted. “I can’t make up my mind what is the explanation. My feeling is that Mr. Wallace has disguised himself in some way, and has been leading, so to speak, a double life. We may already have come across him in some other capacity in this case, so that we should know, could we only ‘spot’ his present identity, what he was after. Until we can link up the two halves of Mr. Wallace, there is no chance of doing anything in the matter.”

“Did you ever see him in the old days?” asked Henry.

“No. That’s the trouble. If I did the case would probably be solved,” answered Shelley. “But you did not finish your story. What happened finally in your little business dealings with the gentleman?”

“Oh, when I couldn’t recover my five pounds, I wrote to him and told him that I wanted nothing more to do with him.”

“Wisest thing to do,” was Shelley’s comment on this.

“I also said that I was compelled to refuse his invitation to spend a week-end with him at his cottage in Penistone, and—”