But mingling with this heterogeneous crowd were old frequenters of the Hexagon in its evil days, mysterious “financiers,” confidence trick men with their touts and runners, slim Latins, with hair like blue satin and the gait of a panther, from the dancing-clubs, and benevolent-looking old ladies, a little too freshly complexioned and a little too bejewelled, who take an interest in any girl that is young and pretty. In brief, the Hexagon was preëminently a resort where the head of a Secret Service organization, to say nothing of one of his principal lieutenants, might expect to make fruitful observations. It was Saturday night and the Hexagon was roaring full. On the dancing-floor, crowded with gliding couples, the red-coated blacks were syncopating themselves into an epileptic frenzy; at the long bar, whence resounded the rattle of the cocktail-shakers, the white-coated attendants were opening oysters as though their lives depended on it; while at the far end of the room, waiters darted incessantly between the thronged tables. Through the long violet curtains that screened the Buffet from the outer lobby new arrivals kept appearing, men and women, old and young, in evening dress and in tweeds, in ermine-collared opera-cloaks and in tailor-mades. And from the merry, noisy, busy, jostling assembly rose, as persistently as the swathes of blue tobacco smoke that drifted aloft on the overheated air, a confused Babel of voices as incessant as the hum of a threshing-floor or the pounding of the sea. “Her name,” said the Chief suddenly, as though he divined his companion’s thoughts, “or at any rate the name by which she chooses to be known, is Madeleine McKenzie. She has been coming here now for a week or more. Nobody knows much about her. Ah!” He nudged Desmond’s elbow. Two youths, very sleek and impeccably attired in evening dress, had sat down at the girl’s table. One of them, a fair-haired, clean-looking boy, was slightly merry with wine. “And now”—unexpectedly the Chief’s voice had become grave—“watch!” His tone quickened Desmond’s whole attention. Ever since the Chief had asked him to dine at the Hexagon on this particular Saturday night, he had been cudgelling his brains to discover with what motive his senior officer had wished to entertain him at this amusing but very bohemian night-resort. Over their Clover Club cocktails at the bar and on various pretexts during dinner itself, Desmond had sought in vain to probe the depths of his host’s thoughts. Now came this summons to watchfulness, stirring in the young man that hunger for adventure which had carried him to such heights of success in the Secret Service.