"Not a sound," cautioned Frank. "They may be listening."
They waited in the shadows for a long time. But evidently Markel had given up the search, his suspicions allayed. Finally a strange sound came from the interior of the mill, a strange whirring sound, followed by the muffled rumble of machinery.
"What's that?" whispered Joe.
They listened. The rumbling sound rose and fell with monotonous regularity. Finally Frank nudged his brother and pointed to one of the boarded windows half way up the side of the mill.
A faint streak of light was apparent through a crack in the boards.
"That must be where their workroom is," Frank whispered.
The sound of machinery in motion continued.
"We've struck them at the right time," said Joe, in a low voice. "They must do their work at night."
"We've got to make sure."
"How can we get inside the mill?"
"The willow tree. We'll have to climb it and drop down on the roof."
"What if they hear us? We won't have a chance to get away."
"They won't hear us," said Frank confidently. "The walls are of stone. Anyway,
