The procedure of Mr. Hurley was astonishing to Audrey; nay, it was unnerving. First he locked the front door and the garden door and pocketed the keys. Then he locked the drawing-room on the passage side and pocketed that key. He instructed Inspector Keeble to remain in the hall at the foot of the stairs. He next went into the kitchen and the sculleries and locked the outer doors in that quarter. Then he descended to the cellars, with Audrey always in his wake. Having searched the cellars and the ground floor, he went upstairs, and examined in turn all the bedrooms with a thoroughness and particularity which caused Audrey to blush. He left nothing whatever to chance, and no dust sheet was undisturbed. Audrey said no word. The detective said no word. But Audrey kept thinking: "He is getting nearer to the tank-room." A small staircase led to the attic floor, upon which were only servants' bedrooms and the tank-room. After he had mounted this staircase and gone a little way along the passage he swiftly and without warning dashed back and down the staircase. But nothing seemed to happen, and he returned. The three doors of the three servants' bedrooms were all ajar. Mr. Hurley passed each of them with a careless glance within. At the end of the corridor, in obscurity, was the door of the tank-room. "What's this?" he asked abruptly. And he knocked nonchalantly on the door of the tank-room. Audrey was acutely alarmed lest Jane Foley should respond, thinking the knock was that of a friend. She saw how idiotic she had been not to warn Jane by means of loud conversation with the detective. "That's the tank-room," she said loudly. "I'm afraid it's locked." "Oh!" murmured Mr. Hurley negligently, and he turned the searchlight of his gaze upon the three bedrooms, which he examined as carefully as he had examined anything in the house. The failure to discover in any cupboard or corner even the shadow of a human being did not appear to discourage him in the slightest degree. In the third bedroom--that is to say, the one nearest the head of the stairs and farthest from the tank-room--he suddenly beckoned to Audrey, who was standing in the doorway. She went within the room and he pushed the door to, without, however, quite shutting it. "Now about the tank-room, Miss Moze," he began quietly. "You say it's locked?" "Yes," said the quaking Audrey. "As a matter of form I'd better just look in. Will you kindly let me have the key?" "I can't," said Audrey. "Why not?" Audrey acquired tranquillity as she went on: "It's at Frinton. Friends of mine there keep a punt on Mozewater, and I let them store the sail and things in the tank-room. There's plenty of room. I give them the key because that's more satisfactory. The tank-room isn't wanted at all, you see, while I'm away from home." "Who are these friends?" "Mr. and Mrs. Spatt," said Audrey at a venture. "I see," said the detective.