When he had travelled a few yards further he glanced at the card indifferently.  Surprised, he turned it over and looked again with interest.  One side of the card was blank; on the other was written in ink three words, “The Green Door.”  And then Rudolf saw, three steps in front of him, a man throw down the card the negro had given him as he passed.  Rudolf picked it up.  It was printed with the dentist’s name and address and the usual schedule of “plate work” and “bridge work” and “crowns,” and specious promises of “painless” operations.

The adventurous piano salesman halted at the corner and considered.  Then he crossed the street, walked down a block, recrossed and joined the upward current of people again.  Without seeming to notice the negro as he passed the second time, he carelessly took the card that was handed him.  Ten steps away he inspected it.  In the same handwriting that appeared on the first card “The Green Door” was inscribed upon it.  Three or four cards were tossed to the pavement by pedestrians both following and leading him.  These fell blank side up.  Rudolf turned them over.  Every one bore the printed legend of the dental “parlours.”

Rarely did the arch sprite Adventure need to beckon twice to Rudolf Steiner, his true follower.  But twice it had been done, and the quest was on.

Rudolf walked slowly back to where the giant negro stood by the case of rattling teeth.  This time as he passed he received no card.  In spite of his gaudy and ridiculous garb, the Ethiopian displayed a natural barbaric dignity as he stood, offering the cards suavely to some, allowing others to pass unmolested.  Every half minute he chanted a harsh, unintelligible phrase akin to the jabber of car conductors and grand opera.  And not only did he withhold a card this time, but it seemed to Rudolf that he received from the shining and massive black countenance a look of cold, almost contemptuous disdain.

The look stung the adventurer.  He read in it a silent accusation that he had been found wanting.  Whatever the mysterious written words on the cards might mean, the black had selected him twice from the throng for their recipient; and now seemed to have condemned him as deficient in the wit and spirit to engage the enigma.

Standing aside from the rush, the young man made a rapid estimate of the building in which he conceived that his adventure must lie.  Five stories high it rose.  A small restaurant occupied the basement.

The first floor, now closed, seemed to house millinery or furs.  The second floor, by the winking electric letters, was the dentist’s.  Above this a polyglot babel of signs struggled to indicate the abodes of palmists, dressmakers, musicians and doctors.  Still higher up draped curtains and milk bottles white on the window sills proclaimed the regions of domesticity.