I am sensible that Mr. Aubrey Gilbert is by no means ideal as the leading juvenile of our piece. The time still demands some explanation why the leading juvenile wears no gold chevrons on his left sleeve. As a matter of fact, our young servant of the Grey-Matter Agency had been declined by a recruiting station and a draft board on account of flat feet; although I must protest that their flatness detracts not at all from his outward bearing nor from his physical capacity in the ordinary concerns of amiable youth. When the army "turned him down flat," as he put it, he had entered the service of the Committee on Public Information, and had carried on mysterious activities in their behalf for over a year, up to the time when the armistice was signed by the United Press. Owing to a small error of judgment on his part, now completely forgotten, but due to the regrettable delay of the German envoys to synchronize with over-exuberant press correspondents, the last three days of the war had been carried on without his active assistance. After the natural recuperation necessary on the 12th of November, he had been re-absorbed by the Grey-Matter Advertising Agency, with whom he had been connected for several years, and where his sound and vivacious qualities were highly esteemed. It was in the course of drumming up post-war business that he had swung so far out of his ordinary orbit as to call on Roger Mifflin. Perhaps these explanations should have been made earlier.  
At any rate, Aubrey woke that Saturday morning, about the time Titania began to dust the pavement-boxes, in no very world-conquering humour. As it was a half-holiday, he felt no compunction in staying away from the office. The landlady, a motherly soul, sent him up some coffee and scrambled eggs, and insisted on having a doctor in to look at his damage. Several stitches were taken, after which he had a nap. He woke up at noon, feeling better, though his head still ached abominably. Putting on a dressing gown, he sat down in his modest chamber, which was furnished chiefly with a pipe-rack, ash trays, and a set of O. Henry, and picked up one of his favourite volumes for a bit of solace. We have hinted that Mr. Gilbert was not what is called "literary." His reading was mostly of the newsstand sort, and Printer's Ink, that naive journal of the publicity professions. His favourite diversion was luncheon at the Advertising Club where he would pore, fascinated, over displays of advertising booklets, posters, and pamphlets with such titles as Tell Your Story in Bold-Face. He was accustomed to remark that "the fellow who writes the Packard ads has Ralph Waldo Emerson skinned three ways from the Jack." Yet much must be forgiven this young man for his love of O. Henry. He knew, what many other happy souls have found, that O. Henry is one of those rare and gifted tellers of tales who can be read at all times. No matter how weary, how depressed, how shaken in morale, one can always find enjoyment in that master romancer of the Cabarabian Nights. "Don't talk to me of Dickens' Christmas Stories," Aubrey said to himself, recalling his adventure in Brooklyn. "I'll bet O. Henry's Gift of the Magi beats anything Dick ever laid pen to. What a shame he died without finishing that Christmas story in Rolling Stones! I wish some boss writer like Irvin Cobb or Edna Ferber would take a hand at finishing it. If I were an editor I'd hire someone to wind up that yarn. It's a crime to have a good story like that lying around half written."
 
He was sitting in a soft wreath of cigarette smoke when his landlady came in with the morning paper.
 
"Thought you might like to see the Times, Mr. Gilbert," she said. "I knew you'd been too sick to go out and buy one. I see the President's going to sail on Wednesday."
 
Aubrey threaded his way through the news with the practiced eye of one who knows what interests him. Then, by force of habit, he carefully scanned the advertising pages. A notice in the HELP WANTED columns leaped out at him.
 
 
WANTED—For temporary employment at Hotel Octagon, 3 chefs, 5 experienced cooks, 20 waiters. Apply chef's office, 11 P.M. Tuesday.
 
 
"Hum," he thought. "I suppose, to take the place of those fellows who are going to sail on the George Washington to cook for Mr. Wilson. That's a grand ad for the Octagon, having their kitchen staff chosen for the President's trip. Gee, I wonder why they don't play that up in some real space? Maybe I can place some copy for them along that line."
 
An idea suddenly occurred to him, and he went over to the chair where he had thrown his overcoat the night before. From the pocket he took out the cover of Carlyle's Cromwell, and looked at it carefully.
 
"I wonder what the jinx is on this book?" he thought. "It's a queer thing the way that fellow trailed me last night—then my finding this in the drug store, and getting that crack on the bean. I wonder if that neighbourhood is a safe place for a girl to work in?"
 
He paced up and down the room, forgetting the pain in his head.
 
"Maybe I ought to tip the police off about this business," he thought. "It looks wrong to me. But I have a hankering to work the thing out on my own. I'd have a wonderful stand-in with old man Chapman if I saved that girl from anything.… I've heard of gangs of kidnappers.… No, I don't like the looks of things a little bit. I think that bookseller is half cracked, anyway. He doesn't believe in advertising! The idea of Chapman trusting his daughter in a place like that——"
 
The thought of playing knight errant to something more personal and romantic than an advertising account was irresistible. "I'll slip over to Brooklyn as soon as it gets dark this evening," he said to himself. "I ought to be able to get a room somewhere along that street, where I can watch that bookshop without being seen, and find out what's haunting it. I've got that old .22 popgun of mine that I used to use up at camp. I'll take it along. I'd like to know more about Weintraub's drug store, too. I didn't fancy the map of Herr Weintraub, not at all. To tell the truth, I had no idea old man Carlyle would get mixed up in anything as interesting as this."
 
He found a romantic exhilaration in packing a handbag. Pyjamas, hairbrushes, toothbrush, toothpaste—("What an ad it would be for the Chinese Paste people," he thought, "if they knew I was taking a tube of their stuff on this adventure!")—his .22 revolver, a small green box of cartridges of the size commonly used for squirrel-shooting, a volume of O. Henry, a safety razor and adjuncts, a pad of writing paper.… At least six nationally advertised articles, he said to himself, enumerating his kit. He locked his bag, dressed, and went downstairs for lunch. After lunch he lay down for a rest, as his head was still very painful. But he was not able to sleep. The thought of Titania Chapman's blue eyes and gallant little figure came between him and slumber. He could not shake off the conviction that some peril was hanging over her. Again and again he looked at his watch, rebuking the lagging dusk. At half-past four he set off for the subway. Half-way down Thirty-third Street a thought struck him. He returned to his room, got out a pair of opera glasses from his trunk, and put them in his bag.
 
It was blue twilight when he reached Gissing Street. The block between Wordsworth Avenue and Hazlitt Street is peculiar in that on one side—the side where the Haunted Bookshop stands—the old brownstone dwellings have mostly been replaced by small shops of a bright, lively character. At the Wordsworth Avenue corner, where the L swings round in a lofty roaring curve, stands Weintraub's drug store; below it, on the western side, a succession of shining windows beacon through the evening. Delicatessen shops with their appetizing medley of cooked and pickled meats, dried fruits, cheeses, and bright coloured jars of preserves; small modistes with generously contoured wax busts of coiffured ladies; lunch rooms with the day's menu typed and pasted on the outer pane; a French rotisserie where chickens turn hissing on the spits before a tall oven of rosy coals; florists, tobacconists, fruit-dealers, and a Greek candy-shop with a long soda fountain shining with onyx marble and coloured glass lamps and nickel tanks of hot chocolate; a stationery shop, now stuffed for the holiday trade with Christmas cards, toys, calendars, and those queer little suede-bound volumes of Kipling, Service, Oscar Wilde, and Omar Khayyam that appear every year toward Christmas time—such modest and cheerful merchandising makes the western pavement of Gissing Street a jolly place when the lights are lit. All the shops were decorated for the Christmas trade; the Christmas issues of the magazines were just out and brightened the newsstands with their glowing covers. This section of Brooklyn has a tone and atmosphere peculiarly French in some parts: one can quite imagine oneself in some smaller Parisian boulevard frequented by the petit bourgeois. Midway in this engaging and animated block stands the Haunted Bookshop. Aubrey could see its windows lit, and the shelved masses of books within. He felt a severe temptation to enter, but a certain bashfulness added itself to his desire to act in secret. There was a privy exhilaration in his plan of putting the bookshop under an unsuspected surveillance, and he had the emotion of one walking on the frontiers of adventure.
 
So he kept on the opposite side of the street, which still maintains an unbroken row of quiet brown fronts, save for the movie theatre at the upper corner, opposite Weintraub's. Some of the basements on this side are occupied now by small tailors, laundries, and lace-curtain cleaners (lace curtains are still a fetish in Brooklyn), but most of the houses are still merely dwellings. Carrying his bag, Aubrey passed the bright halo of the movie theatre. Posters announcing THE RETURN OF TARZAN showed a kind of third chapter of Genesis scene with an Eve in a sports suit. ADDED ATTRACTION, Mr. AND Mrs. SIDNEY DREW, he read.
 
A little way down the block he saw a sign VACANCIES in a parlour window. The house was nearly opposite the bookshop, and he at once mounted the tall steps to the front door and rang.
 
A fawn-tinted coloured girl, of the kind generally called "Addie," arrived presently. "Can I get a room here?" he asked. "I don't know, you'd better see Miz' Schiller," she said, without rancour. Adopting the customary compromise of untrained domestics, she did not invite him inside, but departed, leaving the door open to show that there was no ill will.
 
Aubrey stepped into the hall and closed the door behind him. In an immense mirror the pale cheese-coloured flutter of a gas jet was remotely reflected. He noticed the Landseer engraving hung against wallpaper designed in facsimile of large rectangles of gray stone, and the usual telephone memorandum for the usual Mrs. J. F. Smith (who abides in all lodging houses) tucked into the frame of the mirror. Will Mrs. Smith please call Stockton 6771, it said. A carpeted stair with a fine old mahogany balustrade rose into the dimness. Aubrey, who was thoroughly familiar with lodgings, knew instinctively that the fourth, ninth, tenth, and fourteenth steps would be creakers. A soft musk sweetened the warm, torpid air: he divined that someone was toasting marshmallows over a gas jet. He knew perfectly well that somewhere in the house would be a placard over a bathtub with the legend: Please leave this tub as you would wish to find it. Roger Mifflin would have said, after study............