"It is a point to remember," said Quarles. "We may have to come back to it if we find no other way out of the difficulty. The diamonds were seldom worn, therefore we may assume that any question of suiting the particular dress Lady Leconbridge had on that night is beside the question. For some reason her husband wished her to wear the diamonds on this occasion. Now, if he had reason to suppose that the jewels were not in the safe, his determination is explained, also his annoyance that his son should attempt to thwart him by agreeing with Lady Leconbridge. However, the diamonds were forthcoming, and at a certain moment the Duchess of Exmoor is able to say that Lady Leconbridge was wearing them. Five minutes later they had disappeared. You make a point of the fact that expert thieves were not at work that night, Wigan. Do you imagine that an amateur could take the jewels from the lady's neck without her knowing it?" "You must not lay too much stress upon my point about the expert thieves," I said. "Some gang we know nothing about may have been at work. It certainly is possible to remove a necklace without the wearer being aware of the fact, especially if her mind is fully occupied at the time. In a few moments, no doubt, some movement of her body would have caused Lady Leconbridge to discover the loss, but before this happened her husband was beside her." "With the banker," said Quarles. "It was at the moment that he brought up Hartmann to present him to his wife that he noticed the diamonds were missing. Is it not possible that Hartmann and the diamonds were in some way connected in his mind?" "Possible, of course, but----" "Remember, Wigan, Lord Leconbridge did not mention the substitution of the diamonds for the pearls to you--a curious omission. I have a theory that the stones were to be a demonstration, a proof of something, and that Lord Leconbridge's irritation arises from the fact that he has not been able to give this proof." "Proof of what?" "Ah! that's the question, Wigan; and we have nothing at present to help us to an answer." "You don't suppose Hartmann was responsible for the jewels not being there?" "I have no fact to support such a theory." "Do you suggest that Lady Leconbridge was as anxious that Hartmann should not see the jewels as her husband was that he should?" "I have not made such a suggestion. Since Leconbridge did not tell his wife why he wanted her to wear the diamonds, he probably did not prepare her for Hartmann's introduction. It is difficult to see what time she would have to rob herself and conceal the spoil." "Is Lord Leconbridge a poor man?" Zena asked. "No," I answered; "although I dare say he has plenty of use for his money." "Perhaps he wanted to sell the diamonds." "It is possible," said Quarles. "The stones were a means to some end. Just hand me paper and a pencil, Wigan. My theory grows. Is Lady Leconbridge still in town?"