A simple misdialed telephone call plunges brothers Frank and Joe Hardy into a high-stakes conspiracy involving national security and stolen military technology. When the boys overhear the cryptic phrase "Bombay Boomerang" during a crossed connection to the Pentagon, they find themselves targeted by a dangerous organization. Simultaneously, they must navigate a separate, lethal threat against their father, Fenton Hardy, who is investigating a series of mercury thefts at the Baltimore harbor. The narrative follows a fast-paced, third-person perspective as the brothers connect these disparate threads to prevent a catastrophic attack on the United States.

This entry in the long-running Hardy Boys series maintains the established formula of fast-paced mystery and adolescent adventure that defines the franchise. The narrative relies on the familiar camaraderie between Frank and Joe to drive the investigation forward through increasingly perilous situations. Readers typically engage with this work for its straightforward plotting and the classic appeal of the brothers' detective exploits. The book functions as a quintessential example of mid-century juvenile mystery fiction, prioritizing action and clear-cut moral stakes over complex character development.