Consequently, when he found there was no legal authority to be given him in unravelling the mystery of the diamond robbery, he determined to investigate it on his own account, in order to satisfy his curiosity. To a casual spectator, it appeared to be a mere vulgar burglary, in which the thieves had got off with their plunder, and until his interview with Caprice the detective had supposed it to be so. But when he went over in his own mind the peculiar circumstances of that interview, he saw there was a complicated criminal case to be investigated, so he set himself to work to unravel the mystery, and gratify his inquiring mind. In the first place, he drew up a statement of the case pure and simple, and then, deducing different theories from the circumstances, he tried to get a point from whence to start. He placed his ideas in the form of questions and answers, as follows:-- _Q_. Was Villiers outside on the verandah when Caprice mentioned where her diamonds were kept? _A_. To all appearances he was. _Q_. Had he any inducement to steal the diamonds? _A_. Undoubtedly. He was poor, and wanted money, proved by his calling on Caprice and asking for some. He said he would be revenged because she did not give him more than a sovereign, and there would be no sweeter revenge than to steal her diamonds, as it would punish her, and benefit himself. _Q_. Did he know the room where the diamonds were kept? _A_. Yes. Caprice said her bedroom, and as Villiers had been several times to the house before, he knew where it was. _Q_. Did Caprice know Villiers had stolen her jewels? _A_. Extremely probably, hence her refusal to prosecute, as he was the husband of Madame Midas, whom she had treated so basely. The refusal to prosecute Villiers might be, in Caprice's opinion, an act of expiation. When he had got thus far, Naball paused. After all, this was pure theory. He had not a single well authenticated fact to go on, but all the circumstances of the case seemed to point to Villiers, so he determined to go on the trail of Villiers, and find out what he was doing. Mr. Villiers had of late been under the espionage of the police, owing to some shady transactions with which he was connected, so Naball knew exactly where to find him, and, putting on an overcoat, he sallied forth in the direction of the slums in Little Bourke Street, with the intention of calling on a Chinaman named Ah Goon, who kept an opium den in that unsavoury locality. To his drinking habits Villiers now added that of being a confirmed opium smoker, and was on terms of intimacy with Ah Goon, in whose den he was accustomed to pass his evenings. Naball therefore intended to watch for Villiers, and find out, if possible, when, owing to drink and opium combined, he was not master of himself, what he had done on the night of the robbery after leaving Caprice.