On Saturday evening, about nine o’clock, Mr. Briggs had come to his place and told him that Mr. Lacey, who knew about the key arrangement, had rung him up to say that a Mr. Martin was coming to inspect the drains. Mr. Lacey was to have met him at two o’clock, but would be delayed. Would Mr. Briggs keep a lookout for him and give him the keys. Mr. Briggs had promised to do so, and his daughter Marjorie had seen Mr. Martin, who had promised to bring back the keys, but had not done so. Mr. Briggs had forgotten all about them until the evening, and then, finding that the door of Number 407 was securely locked, had supposed that Mr.