Gissing Street will not soon forget the explosion at the Haunted Bookshop. When it was learned that the cellar of Weintraub's pharmacy contained just the information for which the Department of Justice had been looking for four years, and that the inoffensive German-American druggist had been the artisan of hundreds of incendiary bombs that had been placed on American and Allied shipping and in ammunition plants—and that this same Weintraub had committed suicide when arrested on Bromfield Street in Boston the next day—Gissing Street hummed with excitement. The Milwaukee Lunch did a roaring business among the sensation seekers who came to view the ruins of the bookshop. When it became known that fragments of a cabin plan of the George Washington had been found in Metzger's pocket, and the confession of an accomplice on the kitchen staff of the Octagon Hotel showed that the bomb, disguised as a copy of one of Woodrow Wilson's favourite books, was to have been placed in the Presidential suite of the steamship, indignation knew no bounds. Mrs. J. F. Smith left Mrs. Schiller's lodgings, declaring that she would stay no longer in a pro-German colony; and Aubrey was able at last to get a much-needed bath.  
For the next three days he was too busy with agents of the Department of Justice to be able to carry on an investigation of his own that greatly occupied his mind. But late on Friday afternoon he called at the bookshop to talk things over.
 
The debris had all been neatly cleared away, and the shattered front of the building boarded up. Inside, Aubrey found Roger seated on the floor, looking over piles of volumes that were heaped pell-mell around him. Through Mr. Chapman's influence with a well-known firm of builders, the bookseller had been able to get men to work at once in making repairs, but even so it would be at least ten days, he said, before he could reopen for business. "I hate to lose the value of all this advertising," he lamented. "It isn't often that a second-hand bookstore gets onto the front pages of the newspapers."
 
"I thought you didn't believe in advertising," said Aubrey.
 
"The kind of advertising I believe in," said Roger, "is the kind that doesn't cost you anything."
 
Aubrey smiled as he looked round at the dismantled shop. "It seems to me that this'll cost you a tidy bit when the bill comes in."
 
"My dear fellow," said Roger, "This is just what I needed. I was getting into a rut. The explosion has blown out a whole lot of books I had forgotten about and didn't even know I had. Look, here's an old copy of How to Be Happy Though Married, which I see the publisher lists as 'Fiction.' Here's Urn Burial, and The Love Affairs of a Bibliomaniac, and Mistletoe's Book of Deplorable Facts. I'm going to have a thorough house-cleaning. I'm thinking seriously of putting in a vacuum cleaner and a cash register. Titania was quite right, the place was too dirty. That girl has given me a lot of ideas."
 
Aubrey wanted to ask where she was, but didn't like to say so point-blank.
 
"There's no question about it," said Roger, "an explosion now and then does one good. Since the reporters got here and dragged the whole yarn out of us, I've had half a dozen offers from publishers for my book, a lyceum bureau wants me to lecture on Bookselling as a Form of Public Service, I've had five hundred letters from people asking when the shop will reopen for business, and the American Booksellers' Association has invited me to give an address at its convention next spring. It's the first recognition I've ever had. If it weren't for poor dear old Bock—— Come, we've buried him in the back yard. I want to show you his grave."
 
Over a pathetically small mound near the fence a bunch of big yellow chrysanthemums were standing in a vase.
 
"Titania put those there," said Roger. "She says she's going to plant a dogwood tree there in the spring. We intend to put up a little stone for him, and I'm trying to think of an inscription, I thought of De Mortuis Nil Nisi Bonum, but that's a bit too flippant."
 
The living quarters of the house had not been damaged by the explosion, and Roger took Aubrey back to the den. "You've come just at the right time," he said. "Mr. Chapman's coming to dinner this evening, and we'll all have a good talk. There's a lot about this business I don't understand yet."
 
Aubrey was still keeping his eye open for a sign of Titania's presence, and Roger noticed his wandering gaze.
 
"This is Miss Chapman's afternoon off," he said. "She got her first salary to-day, and was so much exhilarated that she went to New York to blow it in. She's out with her father. Excuse me, please, I'm going to help Helen get dinner ready."
 
Aubrey sat down by the fire, and lit his pipe. The burden of his meditation was that it was just a week since he had first met Titania, and in all that week there had been no waking moment when he had not thought of her. He was wondering how long it might take for a girl to fall in love? A man—he knew now—could fall in love in five minutes, but how did it work with girls? He was also thinking what unique Daintybits advertising copy he could build (like all ad men he always spoke of building an ad, never of writing one) out of this affair if he could only use the inside stuff.
 
He heard a rustle behind him, and there she was. She had on a gray fur coat and a lively little hat. Her cheeks were delicately tinted by the winter air. Aubrey rose.
 
"Why, Mr. Gilbert!" she said. "Where have you been keeping yourself when I wanted to see you so badly? I haven't seen you, not to talk to, since last Sunday."
 
He found it impossible to say anything intelligible. She threw off her coat, and went on, with a wistful gravity that became her even more than smiles:
 
"Mr. Mifflin has told me some more about what you did last week—I mean, how you took a room across the street and spied upon that hateful man and saw through the whole thing when we were too blind to know what was going on. And I want to apologize for the silly things I said that Sunday morning. Will you forgive me?"
 
Aubrey had never felt his self-salesmanship ability at such a low ebb. To his unspeakable horror, he felt his eyes betray him. They grew moist.
 
"Please don't talk like that," he said. "I had no right to do what I did, anyway. And I was wrong in what I said about Mr. Mifflin. I don't wonder you were angry."
 
"Now surely you're not going to deprive me of the pleasure of thanking you," she said. "You know as well as I do that you saved my life—all our lives, that night. I guess you'd have saved poor Bock's, too, if you could." Her eyes filled with tears.
 
"If anybody deserves credit, it's you," he said. "Why, if it hadn't been for you they'd have been away with that suitcase and probably Metzger would have got his bomb on board the ship and blown up the President——"
 
"I'm not arguing with you," she said. "I'm just thanking you."
 
It was a happy little party that sat down in Roger's dining room that evening. Helen had prepared Eggs Samuel Butler in Aubrey's honour, and Mr. Chapman had brought two bottles of champagne to pledge the future success of the bookshop. Aubrey was called upon to announce the result of his conferences with the secret service men who had been looking up Weintraub's record.
 
"It all seems so simple now," he said, "that I wonder we didn't see through it at once. You see, we all made the mistake of assuming that German plotting would stop automatically when the armistice was signed. It seems that this man Weintraub was one of the most dangerous spies Germany had in this country. Thirty or forty fires and explosions on our ships at sea are said to have been due to his work. As he had lived here so long and taken out citizen's papers, no one suspected him. But after his death, his wife, whom he had treated very brutally, gave way and told a great deal about his activities. According to her, as soon as it was announced that the President would go to the Peace Conference, Weintraub made up his mind to get a bomb into the President's cabin on board the George Washington. Mrs. Weintraub tried to dissuade him from it, as she was in secret opposed to these murderous plots of his, but he threatened to kill her if she thwarted him. She lived in terror of her life. I can believe it, for I remember her face when her husband looked at her.
 
"Of course to make the bomb was simple enough for Weintraub. He had an infernally complete laboratory in the cellar of his house, where he had made hundreds. The problem was, how to make a bomb that would not look suspicious, and how to get it into the President's private cabin. He hit on the idea of binding it into the cover of a book. How he came to choose that particular volume, I don't know."
 
"I think probably I gave him the idea quite innocently," said Roger. "He used to come in here a good deal and one day he asked me whether Mr. Wilson was a great reader. I said that I believed he was, and then mentioned the Cromwell, which I had heard was one of Wilson's favourite books. Weintraub was much interested and said he must read the book some day. I remember now that he stood in that alcove for some time, looking over it."
 
"Well," said Aubrey, "it must have seemed to him that luck was playing into his hands. This man Metzger, who had been an assistant chef at the Octagon for years, was slated to go on board the George Washington with the party of cooks from that hotel who were to prepare the President's meals. Weintraub was informed of all this from someone higher up in the German spy organization. Metzger, who was known as Messier at the hotel, was a very clever chef, and had fake passports as a Swiss citizen. He was another tool of the organization. By the original scheme there would have been no direct communication between Weintraub and Metzger, but the go-between was spotted by the Department of Justice on another count, and is now behind bars at Atlanta.
 
"It seems that Weintraub had conceived the idea that the least suspicious way of passing his messages to Metzger would be to slip them into a copy of some book—a book little likely to be purchased—in a second-hand bookshop. Metzger had been informed what the book was, but—perhaps owing to the unexpected removal of the go-between—did not know in which shop he was to find it. That explains why so many booksellers had inquiries from him recently for a copy of the Cromwell volume.
 
"Weintraub, of course, was not at all anxious to have any direct dealings with Metzger, as the druggist had a high regard for his own skin. When the chef was finally informed where the bookshop was in which he was to see the book, he hurried over here. Weintraub had picked out this shop not only because it was as unlikely as any place on earth to be suspected as a channel of spy codes, but also because he had your confidence and could drop in frequently without arousing surprise. The first time Metzger came here happened to be the night I dined with you, as you remember."
 
Roger nodded. "He asked for the book, and to my surprise, it wasn't there."
 
"No: for the excellent reason that Weintraub had taken it some days before, to measure it so he could build his infernal machine to fit, and also to have it rebound. He needed the original binding as a case for his bomb. The following night, as you told me, it came back. He brought it himself, having provided himself with a key to your front door."
 
"It was gone again on Thursday night, when the Corn Cob Club met here," said Mr. Chapman.
 
"Yes, that time Metzger had taken it," said Aubrey. "He misunderstood his instructions, and thought he was to steal the book. You see, owing to the absence of their third man, they were working at cross purposes. Metzger, I think, was only intended to g............