The Secret Passage Author:Kathleen Pennell While housesitting at the Funderburg home, Amy Jo and Becky discover a hidden door leading to a series of underground tunnels. Strange markings on the tunnel wall, visible only with a black light, lead them further and further into the passageways where the Pony Investigators uncover a fiendish plot. Before they can escape the tunnel to warn the... more » police, the girls are caught in a trap where there seems no possible way to escape.« less