After venturing into the woods, the Hardy's were spotted by the gang of Ex-cons and were forced into a waterfall, leading into a river. They hid there and waited until the gang left. The Hardy boys decided to get Chet, their pal, and the only one currently working for the bridge company. They searched and searched for a sign of the gang until finally, they found their hideout. The gang's hideout was inside the structure of a spiral bridge. They planned to attack quietly, with Frank staying behind. As Joe and Chet approached the hideout, they found an opening to a room full of artillery and loud voices from the gang. They jumped in, only to find themselves strapped in bonds moments later. Tony had contacted the police, as well as Phil when they heard gunshots around the spiral bridge. The gang of Ex-cons was held under arrest, except for Willy Teeple. But, the leader of the gang was still hiding nearby, when the police threw smoke bombs into an opening in the rock and out came the leader of the gang! They had captured the Ex-cons! It turned out that Willy Teeple was the one who helped Mr. Hardy escape from the gang and the one who helped report to the police. Finally, the Hardy boys could take a, for the mystery of the spiral bridge had been solved!