Tunnel of Secrets

<b>When Frank and Joe set out to explore caves and tunnels they dig themselves into some dark and dangerous trouble in this Hardy Boys adventure.</b> <p/>When a sinkhole opens up and swallows one of Bayport's historic statues Frank and Joe suspect something--or someone--shady at play. They jump at the chance to investigate; Joe as a member of an urban exploration club and Frank as photographer for the school paper. <p/>But in the thick of their search the boys stumble upon an entire underground city that's been abandoned for years. Now the city is home to a cultish band of criminals who plan to take over Bayport. Frank and Joe are determined to shut down the crooks but after being barreled down by a boulder and nearly squashed by a runaway train they have to wonder: are they in over their heads?