“Positively!” Mr. Debnam was sedately enjoying himself.  “Positively, my dear Inspector, in the arms of a man of extremely dark complexion.  Mr. Vernon was unable to perceive more than this, for the man had his back toward him.  But the light shone fully upon the face of Mrs. Vernon, who appeared pale and exhausted.  She wore a conspicuous motor-coat of civet fur, and it was this which first attracted Mr. Vernon’s attention.  The blow was a very severe one to a man in my client’s state of health; and although I cannot claim that his own conscience was clear, this open violation of the marriage vows outraged the husband—­outraged him.  In fact he was so perturbed, that he stood there shaking, quivering, unable to speak or act, and the car drove away before he had recovered sufficient presence of mind to note the number.”

“In which direction did the car proceed?”

“Toward Victoria Station.”

“Any other particulars?”

“Not regarding the car, its driver, or its occupants; but early on the following morning, Mr. Vernon, very much shaken, called upon me and instructed me to despatch an agent to Perth immediately.  My agent’s report reached me at practically the same time as the news of my client’s death"...

“And his report was?"...

“His report, Inspector, telegraphic, of course, was this:  that no sister of Mrs. Vernon resided at the address; that the place was a cottage occupied by a certain Mrs. Fry and her husband; that the husband was of no occupation, and had no visible means of support”—­he ticked off the points on the long forefinger—­“that the Frys lived better than any of their neighbors; and—­most important of all—­that Mrs. Fry’s maiden name, which my agent discovered by recourse to the parish register of marriages—­was Ann Fairchild.”

“What of that?”

“Ann Fairchild was a former maid of Mrs. Vernon!”

“In short, it amounts to this, then:  Mrs. Vernon, during these various absences, never went to Scotland at all?  It was a conspiracy?”

“Exactly—­exactly, Inspector!  I wired instructing my agent to extort from the woman, Fry, the address to which she forwarded letters received by her for Mrs. Vernon.  The lady’s death, news of which will now have reached him, will no doubt be a lever, enabling my representative to obtain the desired information.”

“When do you expect to hear from him?”

“At any moment.  Failing a full confession by the Frys, you will of course know how to act, Inspector?”

“Damme!” cried Dunbar, “can your man be relied upon to watch them?  They mustn’t slip away!  Shall I instruct Perth to arrest the couple?”

“I wired my agent this morning, Inspector, to communicate with the local police respecting the Frys.”

Inspector Dunbar tapped his small, widely-separated teeth with the end of his fountain-pen.

“I have had one priceless witness slip through my fingers,” he muttered.  “I’ll hand in my resignation if the Frys go!”