"I'd better take these two notes away," he said, beginning to fold up the flimsies. "I shall want you to keep a note of the numbers, in case you are called upon to give evidence." The tailor scratched his head doubtfully, and cast a glance on a policeman passing slowly on the other side of the street. He was beginning to suspect the tall stranger who asserted he was a police officer, and so calmly appropriated money. He was wondering whether, after all, it might not be an ingenious scheme of robbery. He had heard of such things, and the composure of the detective did not comfort him. Green had given no proof of his identity beyond his bare word. With some mumbled excuse the tailor stepped to the door and beckoned to the policeman. With much volubility he explained the situation and his suspicions. The constable listened gravely. He was very young to his duties, and remembered the cautions that had been given him not to accept any one's word where actions were suspicious. "He didn't show you a warrant-card, did he?" he asked. "All right, Mr. Jones, you leave this to me." And he marched importantly into the shop. Green, who had just lit a well-worn brier pipe, and was waiting for the assistant to return in order to pay him the value of the notes, smiled grimly at the apparition of the constable in uniform. He guessed exactly what had happened. "This is the man?" asked the police officer. The tailor nodded, and he went on, addressing Green, "What's this about you taking money and pretending to be a police officer?" He had produced an official notebook and looked very important as he loomed in the doorway, gazing sternly at the detective. "Don't answer any questions unless you want to. You know I shall have to take anything you say down in writing, and it may be used as evidence against you." The situation had a piquant humour that tickled Green. The constable was strictly within his duty, as he had been called in, but the pomposity of his manner betokened that he was very, very young in the service. In a deliberate silence the detective felt in his pocket for a warrant-card that would clear up the mistake. A moment later he was wildly searching in all his pockets without success. For the first time in a lifetime in the service he must have been careless enough to leave it at home. He flourished a number of envelopes inscribed "Chief Detective-Inspector Green, New Scotland Yard, S.W.," but the knowing look of the young constable was emphasised by the cock of the eyebrows. Green never carried official documents except when he was obliged to. "That won't do, old chap," said the constable, in the manner of one well used to the ways of the criminal fraternity. "You don't come that on me. You might have written those envelopes yourself. You'll have to come along."