"There should be some sort of trapdoor here," said Frank quietly. "If there isn't we'll have to lower ourselves over the edge to one of the upper windows. I noticed a small open window around at the front. But there is probably a trapdoor."
The mill roof was not on an abrupt slant, so that the boys were able to make their way along among the shingles without a great deal of difficulty. The roof was in a bad state of repair, and once Frank came upon a wide hole, where the shingles had fallen off and where the wood beneath had rotted away.
But there was no trapdoor.
"We'll tackle that hole in the roof," he decided.
The gap was only about a foot square, but when Frank turned his flashlight on it he saw that immediately beneath them was a sort of attic, the topmost room in the mill.
Quietly, they began enlarging the hole in the roof. Fortunately, the effect of rain and wind and weather had been such as to render the roof extremely weak. The singles broke off easily, and bit by bit they made the hole wider until at last it was a large, black gap.
They did not throw the débris to the ground, but piled it carefully up on the roof near by. The work of enlarging the hole in the roof had taken them some time, as they worked cau-
