"'You might get a little dust from the other side and scatter it about,' said Darby, and before Joan could reply he had scooped a handful of dry, brown dust from the bagroom of the mill and laid it about on the bureau and chairs of the bedroom. 'Now come out for our last patrol,' he said. They went out and studied the mill carefully. As they came around to the house side, keeping carefully in the shadow, Joan looked surprised and pointed to the door by which they had entered.
"'That door's shut,' he said.
"'Well?' asked Darby.
"'We left it ajar.'
"'Oh, the wind!' said Darby, and went up to the door softly, listening for any escaping joker. He rattled the knob and pushed it inward, but the door did not yield. 'Why, you couldn't have left it ajar,' he said, 'it's locked!'
"Joan stared at the house, wondering if it was possible that the window-panes really shone so brightly. And the cobwebs about the blinds, where were they? He could have sworn that the porch was full of dead leaves and sticks when they went in—it was as clean as his hand now.
"'We'll go in by the window, the broken one, at the back,' he said quietly. They went around the house and hunted for the broken window, but did not find it. The window was not only whole but locked. Then Joan set his teeth.
"'The broken window must have been at the mill side,' he said, 'we'll go there.' So they went around and clambered in by a paneless window and went to the bedroom. The room was dim, but they could distinguish objects fairly well. Darby looked queerly at Joan.
"'So you cleared away the dust,' he asked.
"'What dust?' asked Joan. Then he followed Darby's eyes, and where the little piles of brown dust had lain were only clean, bare boards.