Airplane Boys in the Black Woods by E. J. Craine is a captivating tale of adventure and mystery set in the dense jungles of South America. The story follows the Flying Buddies, Bob Caldwell and Jim Austin, two young aviators who find themselves embroiled in a dangerous quest. While their own plane, the "Lark," is under repair, they borrow a helicopter and embark on an exploration mission to study the zone of changing vegetation of the region. Their journey takes an unexpected turn when they encounter a mysterious old man and a group of hostile natives, leading to a series of thrilling events. As the boys navigate the treacherous jungle, they stumble upon a hidden path that suggests the presence of ancient civilizations. Their curiosity is piqued, but their exploration is cut short when they are captured by a gang of ruthless bandits led by a man named Lang. The gang is in search of a valuable report tube, which they mistakenly believe the boys possess. Despite their predicament, Bob and Jim remain resourceful, leaving clues in their trail in hopes of being rescued. The narrative is filled with suspense as the boys are forced to traverse a perilous underground passage, facing natural and man-made obstacles. The tension escalates when a supernatural-like wailing sound terrifies the gang, leading to a tragic accident. Throughout the ordeal, the boys' courage and quick thinking are put to the test as they strive to outwit their captors and find a way back to safety.