"Because," Mr. Thomson explained, "in the trust deed relating to the jewels they can none of them be moved outside the United Kingdom. The Princess would never live in England for more than a month or so in the year, which means that she would be separated from the jewels she loves for the greater part of the time. The Duke has taken every sort of legal opinion, and there is no doubt that if they were stolen from the Castle and returned to him in some foreign country, there is no law which could compel him to bring them back here. That is why the Duke connived at the theft, which you prevented." The elucidation was simple enough but scarcely satisfactory. "If I had known this," I confessed, "I'm afraid my sympathies would have been with the Duke." Mr. Thomson smiled indulgently. "That proves, then," he said, "how wise I am to explain these little affairs with which you chance to become associated, afterwards instead of before. You were acting for the insurance companies, who would have to pay a very large sum to the vested estate if the jewels were stolen from Lorringham. On their behalf," he added, handing me an oblong strip of paper, "I am asked to hand you this cheque for five hundred pounds." I passed it over to Leonard, who usually kept our accounts. "All the same," I observed, "I don't wonder the Duke thought I was a meddlesome idiot." "His Grace has probably forgiven you," Mr. Thomson remarked, "for the Princess has relented at last. If you buy an evening paper on your way home, you will see that they were married by special license this afternoon." We found plenty to think and talk about for the next few minutes. Then Mr. Thomson, who had been leaning back in his chair, watching the stars and listening to the music, electrified us. "In one month," he said, "the year for which you pledged your services to me will be up. At the end of that time we shall say good-by." "You will not want us again?" Rose asked. Mr. Thomson shook his head. "Please do not consider that any reflection upon your efforts," he begged. "During the last ten years I have had assistants in every walk of life. No one has served me more intelligently or on the whole more successfully than you three. The fact of the matter is that I am going to retire." "Retire from what?" I asked him impetuously. "Who are you? What are you? I have never been able to make up my mind whether we have been on the side of the sheep or the goats. How did you become interested, for instance, in this last affair? Did the insurance companies give you a brief? And if so, did they give it to a master criminal, to police headquarters, or to a private detective?"