To Checkley, watching every evening, though not always at the same time, sooner or later the same discovery was certain to come. It happened, in fact, on Friday evening, the day after Athelstan shook hands with Mr. Edmund Gray. On that night he left the office between six and seven, walked to his lodgings in Clerkenwell, made himself a cup of tea, and hurried back to Gray's Inn. Here he planted himself, as usual, close to the passage in the north-east corner of South Square, so that he could slip in on occasion and be effaced. Like many of the detective tribe, or like the ostrich, fount of many fables, he imagined himself by reason of this retreat entirely hidden from the observation of all. Of course the exact contrary was the result. The Policeman regarded him with the liveliest curiosity: the laundresses watched him daily: the newspaper vendor came every evening from the gateway to see what this ancient spy was doing, and why he lurked stealthily in the passage and looked out furtively. He was one of the little incidents or episodes which vary the daily routine of life in the Inn. Many of these occur every year: the people who come to their offices at ten and go away at five know nothing about them: the residents who leave at ten and return at six or seven or twelve know nothing about them. But the Service know: and they talk and conjecture. Here was an elderly man--nay, an old, old man, apparently eighty years of age. What did he want, coming night after night to hide himself in a passage and peer out into the Square? What, indeed? The Policeman, who had done duty in Hyde Park, could tell instructive stories from his own experience about frisky age: the laundresses remembered gentlemen for whom they had 'done,' and pranks with which those gentlemen amused themselves; but no one knew a case parallel to this. Why should an old man stand in the corner and secretly look out into the Square? He generally arrived at half-past seven, and he left his post at nine, when it was too dark to see across the Square. Then he went to the _Salutation_ and enjoyed society, conversation, and a cheerful glass, as you have seen. The time he chose was unfortunate, because Mr. Edmund Gray, when he called at his Chambers, generally did so at half-past six or seven, on his way to the Hall of Science, Kentish Town. Therefore, Checkley might have gone on watching for a long time--say an æon--watching and waiting in vain. But an accident happened which rewarded him richly for all his trouble. It was on Friday. Elsie, provided by this time with a latch-key to the Chambers, arrived at Gray's Inn at six. She was going to spend the evening with the Master. She walked in, ascended the staircase--Mr. Gray had not yet arrived--opened the door, shut it behind her, and entered the room.