Following a family tragedy, Frank Hardy (16) and his brother Joe (12) are forced to move from the big city to their parents' hometown of Bridgeport for the summer. They stay with their Aunt Trudy. Frank and Joe's quiet summer quickly comes to an end when they discover that their father, Detective Fenton Hardy, has launched a secret investigation. Realizing that their father may have discovered something, the boys take it upon themselves to start an investigation of their own, and suddenly everyone in town is a suspect.