“Where?”

“At the entrance to the Finchley Road tube station.”

“Why did you not tell him to call on you instead of yourself going out?”

“In order as far as possible to prevent him from being late at the office.”

French suddenly remembered that Harrington had entered the office during his visit there on the morning after the crime, and had apologised to Mr. Duke for his late arrival. It had not struck French at the time, but now he recalled that when Mr. Duke had spoken to him of the tragedy he had stated he had heard of it already. Where? French now wondered. Was it merely from the morning paper, or was it from Miss Duke? Or, still more pressing question, had they both known of it on the previous night?

Suddenly a possible theory flashed into his mind, and he sat for a few moments in silence, considering it. Suppose that on the stop near Hatton Garden, Harrington had mentioned that he wanted for some purpose to call at the office, or suppose Miss Duke had asked him to do so, and that he had left her for that purpose. Next morning at breakfast she hears from her father of the murder, and is at once panic stricken about Harrington. She sees that if he admits his visit he may be suspected of the crime, and she sends for him before he reaches the office in order to warn him. Or could it be that, knowing of this hypothetical visit, Miss Duke had herself suspected Harrington, and had sent for him at the earliest possible moment to hear his explanation? French was not satisfied with these suggestions, but he felt more than ever certain these two young people had conspired to hide vital information.

He left the house profoundly dissatisfied, and returning to Hatton Garden, had another interview with Harrington. He pressed the young man as hard as he could, taxing him directly with having been present in the office on the fatal night. This Harrington strenuously denied, and French could get nothing further out of him. He went again into the man’s movements on the night of the crime, but without getting any further light thrown thereon. Harrington said he had walked to his rooms after parting from Miss Duke, but no direct evidence was forthcoming as to the truth or falsehood of his statement.

Suddenly another theory leaped into the detective’s mind, but after careful thought he felt he must reject it. If Vanderkemp were guilty, the whole of these mysterious happenings would be cleared up. Harrington was under a deep debt of gratitude to his uncle, and appeared attached to him. Whether Miss Duke shared, or was endeavouring to share, his feelings, French did not know, but it was certainly possible. Suppose he and Miss Duke, driving home from the East End, had seen Vanderkemp at the end of Hatton Garden. Suppose, moreover, something in the man’s appearance had attracted their attention, something furtive or evil, something unlike his usual expression. This, coupled with the fact that the traveller was supposed to be in Amsterdam, might easily have impelled Harrington to stop the cab to have a word with his uncle. But by the time he had reached the pavement, Vanderkemp had disappeared. The incident would have been dismissed by both as trivial, until next morning at breakfast, when Miss Duke learned of the murder, its significance would become apparent. She might not believe the traveller guilty, but she would recognise that the circumstances required some explanation. Immediately the paramount importance of communicating with Harrington would appear, lest he might incautiously mention that he had seen his uncle virtually on the scene of the murder. She would instantly telephone in the hope of catching her lover before he left his rooms. She could not give her message over the telephone, so she would arrange the meeting. She would instruct Harrington to return to her as soon as possible, so as to hear what had taken place at the office. He would therefore call in the afternoon, and at the interview they would decide that in the uncertainty of the situation, the wedding should be postponed. The supposed flight of Vanderkemp would confirm their suspicions, and would account for the perturbed state of mind which both exhibited.

The theory was so fascinating that next day French once more interviewed Harrington and Miss Duke and put the question directly to them, Had they seen Vanderkemp? But both denied having done so, and baffled and irritated, he wrathfully watched another promising clue petering out before him. He had the two young people shadowed, and spent a considerable time in investigating their past life, but without result.

So the days began to draw out into weeks, and the solution of the mystery seemed as far off as ever.