In this engaging mystery, young detectives Frank and Joe Hardy embark on a quest to find a missing baseball mitt that belongs to their friend, Jason. The mitt, which holds sentimental value and is crucial for an upcoming championship game, mysteriously disappears during practice. As the Hardy boys investigate, they encounter a series of clues and potential suspects, including rival players and a suspicious groundskeeper. Through clever deduction and teamwork, Frank and Joe unravel the mystery, ultimately discovering the surprising truth behind the missing mitt and ensuring their friend is ready for the big game.