"Exactly. Although not quite sober, from a mere glance he was able to detect what you were thinking. Do you wish me to believe, Knox, that this same man had not foreseen what the police would think when Colonel Menendez was found shot within a hundred yards of the garden of the Guest House?"

I was somewhat taken aback, for Harley's argument was strictly logical, and:

"It is certainly very puzzling," I admitted.

"Puzzling!" he exclaimed; "it is maddening. This case is like a Syrian village-mound. Stratum lies under stratum, and in each we meet with evidence of more refined activity than in the last. It seems we have yet to go deeper."

He took out his pipe and began to fill it.

"Tell me about the interview with Madame de Stamer," he directed.

I took a seat facing him, and he did not once interrupt me throughout my account of Inspector Aylesbury's examination of Madame.

"Good," he commented, when I had told how the Inspector was dismissed. "But at least, Knox, he has a working theory, to which he sticks like an express to the main line, whereas I find myself constantly called upon to readjust my perspective. Directly I can enjoy freedom of movement, however, I shall know whether my hypothesis is a house of cards or a serviceable structure."

"Your hypothesis?" I said. "Then you really have a theory which is entirely different from mine?"

"Not entirely different, Knox, merely not so comprehensive. I have contented myself thus far with a negative theory, if I may so express it."

"Negative theory?"

"Exactly. We are dealing, my dear fellow, with a case of bewildering intricacies. For the moment I have focussed upon one feature only."

"What is that?"

"Upon proving that Colin Camber did not do the murder."

"Did not do it?"

"Precisely, Knox. Respecting the person or persons who did do it, I had preserved a moderately open mind, up to the moment that Inspector Aylesbury entered the library with the Lee-Enfield."

"And then?" I said, eagerly.

"Then," he replied, "I began to think hard. However, since I practise what I preach, or endeavour to do so, I must not permit myself to speculate upon this aspect of the matter until I have tested my theory of Camber's innocence."

"In other words," I said, bitterly, "although you encouraged me to unfold my ideas regarding Mrs. Camber, you were merely laughing at me all the time!"

"My dear Knox!" exclaimed Harley, jumping up impulsively, "please don't be unjust. Is it like me? On the contrary, Knox"-he looked me squarely in the eyes-"you have given me a platform on which already I have begun to erect one corner of a theory of the crime. Without new facts I can go no further. But this much at least you have done."

"Thanks, Harley," I murmured, and indeed I was gratified; "but where do your other corners rest?"

"They rest," he said, slowly, "they rest, respectively, upon a bat wing, a yew tree, and a Lee-Enfield charger-loader."

CHAPTER x.x.x

THE SEVENTH YEW TREE

Detective-Inspector Wess.e.x arrived at about five o'clock; a quiet, resourceful man, highly competent, and having the appearance of an ex- soldier. His respect for the attainments of Paul Harley alone marked him a student of character. I knew Wess.e.x well, and was delighted when Pedro showed him into the library.

"Thank G.o.d you are here, Wess.e.x," said Harley, when we had exchanged greetings. "At last I can move. Have you seen the local officer in charge?"

"No," replied the Inspector, "but I gather that I have been requisitioned over his head."

"You have," said Harley, grimly, "and over the head of the Chief Constable, too. But I suppose it is unfair to condemn a man for the shortcoming with which nature endowed him, therefore we must endeavour to let Inspector Aylesbury down as lightly as possible. I have an idea that I heard him return a while ago."

He walked out into the hall to make enquiries, and a few moments later I heard Inspector Aylesbury's voice.

"Ah, there you are, Inspector Aylesbury," said Harley, cheerily. "Will you please step into the library for a moment?"

The Inspector entered, frowning heavily, followed by my friend.

"There is no earthly reason why we should get at loggerheads over this business," Harley continued; "but the fact of the matter is, Inspector Aylesbury, that there are depths in this case to which neither you nor I have yet succeeded in penetrating. You have a reputation to consider, and so have I. Therefore I am sure you will welcome the cooperation of Detective-Inspector Wess.e.x of Scotland Yard, as I do."

"What's this, what's this?" said Aylesbury. "I have made no application to London."

"Nevertheless, Inspector, it is quite in order," declared Wess.e.x. "I have my instructions here, and I have reported to Market Hilton already. You see, the man you have detained is an American citizen."

"What of that?"

"Well, he seems to have communicated with his Emba.s.sy." Wess.e.x glanced significantly at Paul Harley. "And the Emba.s.sy communicated with the Home Office. You mustn't regard my arrival as any reflection on your ability, Inspector Aylesbury. I am sure we can work together quite agreeably."

"Oh," muttered the other, in evident bewilderment, "I see. Well, if that's the way of it, I suppose we must make the best of things."

"Good," cried Wess.e.x, heartily. "Now perhaps you would like to state your case against the detained man?"

"A sound idea, Wess.e.x," said Paul Harley. "But perhaps, Inspector Aylesbury, before you begin, you would be good enough to speak to the constable on duty at the entrance to the Tudor garden. I am anxious to take another look at the spot where the body was found."

Inspector Aylesbury took out his handkerchief and blew his nose loudly, continuing throughout the operation to glare at Paul Harley, and finally:

"You are wasting your time, Mr. Harley," he declared, "as Detective- Inspector Wess.e.x will be the first to admit when I have given him the facts of my case. Nevertheless, if you want to examine the garden, do so by all means."

He turned without another word and stamped out of the library across the hall and into the courtyard.

"I will join you again in a few minutes, Wess.e.x," said Paul Harley, following.

"Very good, Mr. Harley," Wess.e.x answered. "I know you wouldn't have had me down if the case had been as simple as he seems to think it is."

I joined Harley, and we walked together up the gravelled path, meeting Inspector Aylesbury and the constable returning.

"Go ahead, Mr. Harley!" cried the Inspector. "If you can find any stronger evidence than the rifle, I shall be glad to take a look at it."

Harley nodded good-humouredly, and together we descended the steps to the sunken garden. I was intensely curious respecting the investigation which Harley had been so anxious to make here, for I recognized that it was a.s.sociated with something which he had seen from the window of Camber's hut.

He walked along the moss-grown path to the sun-dial, and stood for a moment looking down at the spot where Menendez had lain. Then he stared up the hill toward the Guest House; and finally, directing his attention to the yews which lined the sloping bank:

"One, two, three, four," he counted, checking them with his fingers- "five, six, seven."

He mounted the bank and began to examine the trunk of one of the trees, whilst I watched him in growing astonishment.

Presently he turned and looked down at me.