Books like Footprints Under the Window by Franklin W. Dixon

Frank and Joe Hardy find themselves alone after their famed father disappears. They must stop a plot to steal a critical U.S. space program instrument that has attracted a shadowy espionage ring. Their investigation leads to a South American stowaway who mutters a cryptic warning about "Footprints." The boys trace the strange prints under a window to the stowaway and set off on an international chase that takes them to an isolated island off the coast of South America. There they confront a cruel dictator, uncover a grim jungle secret, and endure a tense vigil in a cemetery before being trapped in the flooded compartment of a wrecked ship. With friend Chet Morton by their side, Frank and Joe use their courage and ingenuity to outwit the mastermind behind the spy ring, delivering a suspenseful and action‑packed adventure for Hardy Boys fans.

First publish date: 1933