when kilsip undertook to educate naball in the business of a detective, he gave him an epigrammatical piece of advice: "cultivate curiosity." this golden rule naball constantly followed, and found it of infinite service to him in his difficult profession. he was always on the lookout for queer cases, and when he discovered one that piqued his curiosity, he never rested until he found out all about it. the red indian follows the trail of his enemy by noting the most trivial signs, which to others with a less highly cultivated instinct would appear worthless. and naball was a social red indian, following up the trail of a mystery by a constant attention to surrounding events. a casual observation, a fleeting expression, a scrap of paper--these were the sign-posts which led him to a satisfactory conclusion, and he never neglected any opportunity of exercising his faculties. by this constant practice he sharpened his senses in a wonderful degree, and cultivated to the highest extent the unerring instinct which he possessed in discovering crimes.

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.

he soon entered little bourke street, and plunged into the labyrinth of slums, which he knew thoroughly. it was a clear, starry night, but the cool, fresh air was tainted in this locality by the foul miasma which pervaded the neighbourhood, and even the detective, accustomed as he was to the place, felt disgusted with the sickly odours that permeated the atmosphere.

ah goon's house was in a narrow right-of-way off one of the larger alleys, and there was a faint candle burning in the window to attract customers. pausing at the door a moment, naball listened to hear if there was any european within. the monotonous chant of a chinese beggar could be heard coming down the alley, and every now and then the screams of two women fighting, while occasionally a number of noisy larrikins would come tramping heavily along, forming a strong contrast to the silent, soft-footed orientals.

pushing open the door, naball entered the den, a small, low-ceilinged room, which was filled with a dull, smoky atmosphere. at the end was a gaudy-looking shrine, all yellow, red, and green, with tinsel flowers, and long red bills with fantastic chinese letters on them in long rows. candles were burning in front of this, and cast a feeble light around--on a pile of bamboo canes and baskets heaped up against the wall; on strange-looking chinese stools of cane-work; on bizarre ivory carvings set on shelves; and on a low raised platform at the end of the room, whereon the opium-smokers reclined. above this ground-floor were two or three other broad, shallow shelves, in each of which a chinaman was lying, sunk deep in an opium slumber; there was also a kerosene lamp on the lower floor, beside which ah goon was reclining, and deftly preparing a pipe of opium for a fat, stolid-looking chinaman, who watched the process with silent apathy.

ah goon looked up as the detective entered, and a bland smile spread over his face as he nodded to him, and went on preparing his pipe, while naball stood watching the queer operation. there was an oil lamp with a clear flame in front of ah goon, who was holding a kind of darning-needle. dipping this into a thick, brown, sticky-looking substance, contained in a small pot, he twirled the needle rapidly, spinning round the glutinous mass like treacle. then he placed it in the flame of the lamp, and turned it slowly round and round for a short time until it was ready; then, having placed it in the small hole of the opium pipe, which he held ready in his other hand, he gave it to his countryman, who received it with a grunt of satisfaction, and, lying back, took the long stem between his lips and inhaled the smoke with long, steady breaths. when his pipe was done, which was accomplished in three or four whiffs, he devoted himself to preparing another, while ah goon arose to his feet to speak to naball.

he was a tall man, with a thin, yellow-skinned, emaciated face, cunning, oblong eyes, and flattish nose. his pigtail, of course--black hair craftily lengthened by thick twisted silk--was coiled on top of his head; and his dress, consisting of a dull blue blouse, wide trousers of the same colour, and thick, white-soled chinese slippers, by no means added to his personal beauty. standing before naball, with an unctuous smile on his face, and his long, slender hands clasped in front of him, ah goon waited for the detective to speak.

naball glanced rapidly round the apartment, and not seeing villiers, addressed himself to the stolid celestial, who was looking slyly at him.

"ah goon, where is the white man who comes here every night?"

"plenty he come allee muchee night--me no have seen," replied ah goon, blinking his black eyes.

"yes, i know that," retorted naball quickly; "but this one is short--black hair and whiskers--smokes opium--drinks a lot--is called villiers."

whether ah goon recognised the gentleman thus elegantly described was doubtful; at all events, he put on a stolid air.

"me no sabee," he answered.

naball held out a half-a crown, upon which ah goon fixed his eyes lovingly.

"where is he?"

the money was too much for ah goon's cupidity, so he gave in.

"him playee fan-tan-ayah!" he answered, in a sing-song voice, "allee same."

"oh!"

mr. naball did not waste any words, but threw the half-crown to the expectant ah goon, and turned towards the door. just as he reached it there was a noise of hurried footsteps outside, and villiers' voice, husky and savage, was heard,--

"ah goon, you yellow devil, where are you?" and there came a heavy kick at the door.

in a moment naball drew back into a shadowy corner, and placed his finger on his lips to ensure silence, a pantomime which the intelligent ah goon understood at once.

villiers opened the door and lurched noisily into the room, stopping for a minute on the threshold, dazed by the yellow, smoky glare.

"here, you, ah goon," he cried, catching sight of the chinaman, "i want some money--more money."

"ah goon no have," murmured that individual, clutching his half-crown.

"i've lost all i had on that infernal fan-tan of yours," shrieked villiers, not heeding him; "but my luck must change--give me another fiver."

"ah goon no have," reiterated the chinaman, edging away from the excited villiers.

"curse your no have," he said fiercely; "why, i've only had twenty pounds from you, and those diamonds were worth fifty."

diamonds! naball pricked up his ears at this. he was winning after all. kitty did not steal her jewels, but this was the thief, or perhaps an accomplice.

"give me more money," cried villiers, lurching forward, and would have laid his hand on the shoulder of the shrinking chinaman, when naball stepped out of his corner.

"what's the matter?" he asked, in his silky voice.

villiers turned on the new-comer with a sudden start, and stared suspiciously at him; but the detective being muffled up in a heavy ulster, with his hat pulled over his eyes, he did not recognise him.

"what do you want?" he said ungraciously.

"nothing," replied naball quickly. "i'm only strolling round the chinese quarter out of curiosity, and heard you rowing this poor devil."

"poor devil!" sneered villiers, with a glance of fury at ah goon, who had complacently resumed his occupation of preparing an opium pipe; "he's rich enough."

"indeed," said the detective, carelessly--"to lend money?"

"what's that to you?" growled villiers, with a snarl. "i s'pose i can borrow money if i like."

"certainly, if you've got good security to give."

villiers glared angrily at the young man.

"don't know what you're talking about," he said sulkily.

"security," explained naball smoothly; means "borrowing money on land, clothes, or--or diamonds."

villiers gave a sudden start, and was about to reply, when the door opened violently, and a bold, handsome woman, dressed in a bright green silk, dashed into the room and swooped down on ah goon.

"well, my dear," she said effusively, "'ere i am; bin to the theatre, and 'ere you are preparing that pisin of yours. oh, i must 'ave one pipe to-night, just one, and--who the blazes are you?" catching sight of the two strangers.

"shut up," said villiers, and made a step towards her, for just on the bosom of her dress sparkled a small crescent of diamonds set in silver. the woman's eyes caught his covetous glance, and she put her hand over the ornament.

"no, you don't," she said scowling. "lay a finger on me and i'll--ah!"

she ended with a stifled cry, for without warning, villiers had sprung on her, and his hands were round her throat. ah goon and another chinaman jumped up and threw themselves on the two, trying to separate them. the woman got villiers' hands off her, and started to sing out freely, so naball began to think of retreating, as the noise would bring all the undesirable bullies of the neighbourhood into the unsavoury den.

while thus hesitating, the woman flung the diamond ornament away from her with an oath, and it fell at naball's feet. in a moment the detective had picked it up and slipped in into his pocket.

villiers, seeing the ornament was gone, flung the woman from him with a howl of fury, and turned to look for it, when the door was burst violently open, and a crowd of chinese, all chattering in their high shrill voices like magpies, surged into the room. ah goon, with many gesticulations, began to explain, villiers to swear, and the woman to shriek, so in the midst of this pandemonium naball slipped away, and was soon walking swiftly down little bourke street, with the diamond ornament safe in his pocket.

"i believe this is one of the stolen jewels," he muttered exultingly, "and villiers was the thief after all. humph! i'm not so sure of that. well, i'll find out the truth when i see how she looks on being shown this little bit of evidence."