Then he took another sheet of paper, headed it “Immediate Jobs,” and then chewed the end of his pen reflectively. What he afterwards wrote was this:

“(1) ? Exhume Wilkinson. See Home Secretary. ? Is cyanide traceable long after death.

“(2) Make sure of facts about Baker’s presence in B.M. when Wilkinson died. ? Find if Baker has alibi on occasion of death of Arnell. P.S.—Alibi not worth much in any case, since poisoned sweet may have been placed in bag some time before.

“(3) See about Arnell’s will—also Wilkinson’s? Is any one beneficiary of both, save Baker, who benefits via Violet Arnell in second case, and directly in first case.

“(4) Does Dr. Crocker of Oxford know anything about these two? Can he help in suggesting motives, since he is apparently a friend of both of them?

“(5) Were there any personal quarrels in which the two men were concerned? Any enemy of the two, apart from mercenary motives.”

He put down his pen and sighed deeply. “The questions seem to be endless,” he murmured. “Suppose I’m trying to theorise too soon. Must wait until I’ve got more facts to work upon. At the moment things look pretty black for Mr. Baker, but then at this stage in the case it’s impossible to go at all deeply into questions of motive, and so on. Where the devil is Cunningham?”

There was a bell on the desk before him, and he pressed it. A constable appeared. “Has Sergeant Cunningham returned yet?” asked Shelley.

“No, sir.”

“Well, when he does, tell him to report to me at once. I shall stay here until his return, as he will have some important information on this case,” Shelley snapped.

“Very well, sir.”

The constable retired, and Shelley studied the document before him—the list of jobs to be immediately done, questions to be settled without delay.

What was there here which he could make up his mind to do straight away? He probably had some hours to waste before Cunningham returned, and he might as well employ those hours in a more or less profitable manner, he told himself.

Then he looked up in pleasant anticipation. Question number four. That could be decided without delay. Dr. Crocker of Oxford might be at home. Anyhow, he could communicate with the Oxford police, and then, if the man was in residence (it was still vacation time, so he might be climbing the Alps, or doing whatever else Oxford dons did in their holidays), he would be able to run down to Oxford on the following morning, and find out what he had to say about his two dead friends.

Shelley drew the telephone towards him. “Get me Oxford police,” he instructed the operator.