A resounding knock on the side door, through which she had entered the library a few minutes before, caused Kitty to start violently and her hand reached out instinctively to catch the mantel-piece to steady herself. For a second she rested her weight against it, then, controlling her nervousness, she thrust the mauve paper into the pocket of her coat and with reluctance moved over to the side door. Callers did not usually announce their presence in that manner. Miss Susan Baird had never permitted what she termed "familiarity," and no friend, no matter what the degree of intimacy, was ever admitted except through the front door. Her dominating character had forced respect for her peculiarities, and Kitty could recall no one, except herself, who had ever cared to cross her aunt in any particular. With her hand on the door-knob, Kitty hesitated. She was alone in the house and in no mood for visitors. Squaring her shoulders, she pulled the door partly open. Inspector Mitchell was standing on the top step of the small "stoop" which led to the brick walk. "Good afternoon, Miss Baird," he said, bowing affably. "Can you spare me a few minutes of your time?" "Why, certainly." Kitty concealed her vexation. The inspector was the last person she had expected to encounter. "Won't you come in?" and she opened the door to a wider extent. Not waiting for him to remove his overcoat, she hurried across the library and picking up a log from the wood basket by the hearth she stirred the fire to a brighter blaze. On facing about, she found the inspector standing in front of the side door and regarding it with fixed attention. "This door does not seem exactly in keeping with this house," he said, as Kitty approached him. "I've never seen a finer example of Colonial architecture, but this--" laying his hand on the upper section of the door--"this resembles a Dutch door." "That is exactly what it is, or rather, what Aunt Susan had it converted into," Kitty explained. "Aunt Susan had a bad attack of inflammatory rheumatism about fifteen years ago; she could not leave the house and sat chiefly in this room. She was devoted to her garden and had this side door cut in half so that she could see outside without having to open the entire door." "And this panel in the upper half of the door?" Mitchell laid his hand on it as he spoke. "Does it open?" "Yes, it is a sliding panel." Kitty stifled a yawn. "The builder's idea of ornamentation, I presume--a door within a door." She smiled. "And rusty with disuse. Oscar has an objection to cleaning brass, or anything in fact that requires 'elbow grease.'" "The _latch_ is discolored," Mitchell amended. With a quick motion of his hand he released the catch and pushed the panel backward. "But there is no sign of rust in the hinges. Judging from the way this panel moves, Miss Baird, it is well oiled. See for yourself."