She resided in a fine brown-stone mansion up town; sported an elegant carriage and a spanking pair of bays, and, to all appearances, possessed an unlimited bank account.

She was sometimes attended on her drives by a gentleman, many years older than herself, who appeared to be something of an invalid, and who, as far as the detective could learn, was engaged in no business whatever.

These latter facts increased his suspicions, for the reason that the woman who had robbed Mr. Palmer had wished to submit her selections to the sanction of an invalid husband.

Disguised as a spruce young coachman, Mr. Rider managed to ingratiate himself with a pretty, but rather vain young servant-girl in Mrs. Vanderheck’s employ, and by means of well-turned compliments, re-enforced now and then with some pretty gift, he managed to keep himself well posted regarding the mistress’ movements and her social engagements, and then he diligently followed up his espionage by frequenting the many receptions and balls which she attended.

At these places she was always magnificently attired and seldom wore any ornaments except diamonds, of which she appeared to possess an endless store, and all were of great beauty and value.

It was at a Delmonico ball, which was given in honor of a person of royal descent, and on the Friday evening preceding Ray Palmer’s visit to Hazeldean, that Mr. Rider found his plans ripe for action and accomplished his great coup de grace.

He had learned, through the pretty servant-girl, that Mrs. Vanderheck was to grace the occasion with her presence and was to be attired in a costume of unusual richness and elegance—­“with diamonds enough to blind you,” the lively and voluble Fanny had boasted to her admirer.

Consequently the detective got himself up in elaborate style, obtained a ticket for the ball by some means best known to himself, and, when the festivities were at their height, slipped in upon the brilliant scene.

He was not long in “spotting” his prey, who was conspicuous in white brocaded velvet and white ostrich tips, while her person was literally ablaze with diamonds.

“Great Scott!” the man muttered, as he ran his keen eye over her gorgeous attire; “it is a mystery to me how any woman dare wear such a fortune upon her person; she is liable to be murdered any day.  Why, she—­Aha!”

His heart gave a sudden leap, and for a moment, as he afterward described his sensations, it seemed as if some one had struck him on the head with a club, for he actually saw stars and grew so dizzy and confused that he could scarcely stand; for—­in the woman’s ears he caught sight of a gleaming pair of crescents!

He soon recovered himself, however, and took a second look.  He had, as we know, been looking for those peculiar ornaments for more than three years, and now he had found them, as he had always believed he should, upon a gay woman of fashion in the midst of fashionable admirers.