"We did indeed," I replied. "We want to know why the Duke was engaged in a conspiracy to steal his own jewels, and why our mission there seemed to be to prevent it."
"Quite a little romance," our host observed. "The Duke, as you may have noticed, is very much in love with the Princess of Chantilly. The Princess is one of those women in whom the love of jewels amounts to a passion. The Lorringham pink pearls are, as you may know, priceless. More than anything in the world the Princess desires to wear those pearls."
"Then why doesn't she acquire them by marrying the Duke?" I asked.
"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."