"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."