Having finished his patrol of the Square itself, he passed along the backs, abutting on a somewhat mean street, for a rather undesirable neighbourhood had built itself around these somewhat stately houses. His perambulations brought him to the back of Number 10, the house to let. His trained eye, accustomed to take in the smallest details, noticed a broken pane of glass in the scullery window. He climbed over the low railing which shut off the back premises from the mean street on which they looked, and peered at the broken window-pane. From a general point of view there was not much in it. Window-panes are broken every day. But this was an empty house, looked after by a somewhat bibulous caretaker of the name of Miles. A hundred chances to one that Miles had stumbled against it, and broken it with his elbow. But although Constable Brown was not very brilliant, he was painstaking and methodical; his mind was slow but tenacious. He did not accept facts at their face value. After peering through the broken pane, he proceeded to further experiments. He lifted the window, and it went up easily. He drew his deductions swiftly. Somebody had entered the empty house. That somebody had smashed the pane in order to get at the latch, had entered the house, later emerged through the window and forgotten to fasten it. But why enter an empty house, where there was nothing to steal except the heavy furniture left by the late tenant, a Mr Washington, who was abroad? Brown knew for a fact from the caretaker that all silver and plate had been lodged at Mr Washington's bank. It was a puzzle. One thing was clear: his duty lay straight before him. He must go over that empty house. A careful examination might reveal something or nothing. But he was a very cautious man, and with no great belief in his own powers. He would not make the examination alone. He blew his whistle for further assistance. In a few seconds, a fellow constable, a smart young fellow, hurried up to him. Brown pointed to the broken pane, the uplifted window. The smart young man projected himself through the open space. Brown followed, explaining as he went. They searched the basement, the ground floor, and the floor above--with no result. "Now for the caretaker," said the younger and the more quick-witted of the two policemen. "He sleeps up at the top," answered Brown. "He generally comes home half-seas over. If a regiment was hammering at the door he would not wake till his sleep was done." They went up to the caretaker's room on the top floor. The bed was empty. Miles had evidently taken a holiday. The young constable grunted. "Seems a reliable sort of chap, doesn't he? I wonder how long he has been away? The house agents can tell us if they have sent any clients to view the house during the last twenty-four hours, and whether they have been able to get in or not. Anyway, for the present, he seems out of this job."