<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?<br><br><b>Author:</b> Franklin W. Dixon<br><b>Publisher:</b> Aladdin Paperbacks<br><b>Published:</b> 10/20/2015<br><b>Pages:</b> 144<br><b>Binding Type:</b> Paperback<br><b>Weight:</b> 0.10lbs<br><b>Size:</b> 7.40h x 5.10w x 0.50d<br><b>ISBN:</b> 9781481438742<br><b>Audience:</b> Ages 9-12<br><br><b>Accelerated Reader:</b><br><b>Reading Level:</b> 5.6<br><b>Point Value:</b> 5<br><b>Interest Level:</b> Middle Grade<br><b>Quiz #/Name: </b>178740 / Tunnel of Secrets<br>