“It’s beyond me how you puzzle these things out,” she said. “It’s brains,” explained Julius. “You get such ideas,” she said in despair. “I wonder you don’t go on the stage.” It was her conviction that the stage was the ultimate goal of all genius; its greatest reward; its most natural line of development. “This Double Dan is certainly a bit of a puzzle, though I’ve worked out bigger problems in my time, mother.” She nodded in agreement. “The way you mended the cistern last week beats me,” she said. “After that I’ll believe anything. Who is this Double Dan?” “He’s a swindler,” said Mr. Superbus, “a parasite of society, a human vampire--but I’ll get him!” “I’m surprised the police don’t go after him,” she said. He was naturally irritated, and his laughter lacked sincerity. “The police! No, mother, the man who’s going to get Double Dan has got to be clever, he’s got to be cunning, he’s got to be artful.” “I don’t know anybody artfuller than you, Julius,” said his wife graciously, and Mr. Superbus accepted the compliment as his right. He might speak disparagingly of the police, as he did; as all private detectives, authors of mystery stories and such-like are in the habit of doing. But his knowledge that Double Dan was in London, the hint that had been whispered up from the underworld that Mr. Gordon Selsbury was to be the new victim; these and a hundred other little pointers of incalculable value came to him fourth-hand from Scotland Yard. After his midday dinner he put on his coat and strolled to Cheynel Gardens. Gordon was out, and he was received by Diana. “Why, of course, you’re Mr.----” “Superbus,” said Julius. “The Roman!” Mr. Superbus confessed to that distinction. He might have added “ultimus Romanorum,” only he was unacquainted with the phrase. Instead he remarked, a little pathetically: “There ain’t many of us left.” “I bet there ain’t,” said Diana. “Sit down and have some tea. You want to see Mr. Selsbury, but he won’t be back for an hour.” “I did and I didn’t,” said Julius the obscure. “What I want to do is to keep a certain eye on a certain fellow.” He did not particularise the eye, but Diana guessed that it might be that which was nearest to her: it looked the less glassy of the two. In the matter of the certain fellow she sought information. “Double Dan--I remember. Who is he, Mr. Superbus?” “Well, ma’am----” “Miss.” “You don’t look it,” he said gallantly, if vaguely. “This Double Dan is a desperado, and is believed to emanate from the West.” “Do you mean West London?” “I mean America,” said Julius, “where most of the desperadoes come from. And go to,” he added, with a recollection of certain past defaulters, whose disappearance had been hampering to him as a bailiff of the court. She listened attentively while Mr. Superbus described the misdoings of the impersonator.