The house where Letitia lived was, of course, a very old one. It had a roof, saggy and mossy, gray shingles in the walls, lilac bushes half hiding the great windows, and a well-sweep in the yard. It was quite a large house, and there were sheds and a great barn attached to it, but they were all on the side. At the back of the house the fields stretched away for acres, and there were no outbuildings. The little green door was at the very back of the house, toward the fields, in a room opening out of the kitchen. It was called the cheese-room, because Letitia's grandmother, who had made cheeses, had kept them there. She fancied she could smell cheese, though none had been there for years, and it was used now only for a lumber-room. She always sniffed hard for cheese, and then she eyed the little green door with wonder and longing. It was a small green door, scarcely higher than her head. A grown person could not have passed through without stooping almost double. It was very narrow, too, and no one who was not slender could have squeezed through it. In this door there was a little black keyhole, with no key in it, but it was always locked. Letitia knew that her Aunt Peggy kept the key in some very safe place, but she would never show it to her, nor unlock the door. "It is not best for you, my dear," she always replied, when Letitia teased her; and when Letitia begged only to know why she could not go out of the door, she made the same reply, "It is not best for you, my dear." Sometimes, when Aunt Peggy was not by, Letitia would tease the old maid-servant about the little green door, but she always seemed both cross and stupid, and gave her no satisfaction. She even seemed to think there was no little green door there; but that was nonsense, because Letitia knew there was. Her curiosity grew greater and greater; she took every chance she could get to steal into the cheese-room and shake the door softly, but it was always locked. She even tried to look through the key-hole, but she could see nothing. One thing puzzled her more than all, and that was that the little green door was on the inside of the house only, and not on the outside. When Letitia went out in the field behind the house, there was nothing but the blank wall to be seen. There was no sign of a door in it. But the cheese-room was certainly the last room in the house, and the little green door was in the rear wall. When Letitia asked her Great-aunt Peggy to explain that, she only got the same answer: "It is not best for you to know, my dear." Letitia studied the little green door more than she studied her lesson-books, but she never got any nearer the solution of the mystery, until one Sunday morning in January. It was a very cold day, and she had begged hard to stay home from church. Her Aunt Peggy and the maid-servant, old as they were, were going, but Letitia shivered and coughed a little and pleaded, and finally had her own way.