It is bad enough to have to follow a railroad through a twisting, winding valley with barely enough room to handle the plane, but when that railroad runs into a tunnel, then the leader of the Flight is up against it to know just what to do. Bill had this situation confronting him. He did not want to back-track down the valley, for the clouds by this time might have settled down and shut off all possibility of getting out. Something had to be done, however, and must be done at once. The mouth of the tunnel was getting closer and closer.