Plot

Based on a true-story - A Plumm Summer tells the remarkable tale of two young brothers, Elliott and Rocky Plumm, who go head-to-head with the FBI in order to crack the "frog-napping" case and get their beloved TV puppet, Froggy Doo back on the air, all the while become local heroes and best friends.

The film is based on a real event that occurred in 1968 in Billings, Montana, the hometown of screenwriter T. J. Lynch. A popular locally produced children's television show, Happy Herb & Froggy Doo, features magician Happy Herb (Henry Winkler) and his wisecracking marionette sidekick, Froggy Doo. Froggy Doo is stolen and held for ransom, and the Federal Bureau of Investigation (FBI) is called in to investigate. Elliott Plumm (Chris Massoglia) used to watch the show, but now feels he is too grown up to do so any longer. His five-year-old brother, Rocky, is a Froggy Doo fan, however. Their father, Mick Plumm (William Baldwin), is a recovering alcoholic and unemployed ex-boxer who believes Elliott's birth prevented him from going to the Olympic Games 12 years earlier. Mick's emotionally distant relationship with Elliott is causing Elliott to become emotionally troubled. Their mother, Roxie Plumm (Lisa Guerrero), is the only breadwinner in the family, and keeping her husband sober and attending to her job means she has little time for her children.

Elliott shows little interest in the kidnapping. Shortly thereafter, however, Haley Dubois (Morgan Flynn) and her father arrive in their run-down mobile home and move in next door. Haley's father is the new deputy sheriff in town, and Haley is entranced by the mystery surrounding the kidnapping of Froggy Doo. Elliott quickly begins to fall in love with Haley, and soon he agrees to help Haley and Rocky find Froggy Doo in order to win Haley's heart. The three kids have to find the marionette before the two bumbling FBI agents, Hardigan (Peter Scolari) and Brinkman (Rick Overton) can do so. Elliott, Haley, and Rocky's list of suspects include the local bully, a store clerk, and Happy Herb's wife Viv (Brenda Strong). As the kids pursue the case, Elliott and Rocky's brotherly bond strengthens, and Elliott realizes he might not only win back the love of his father but provide his family with the substantial reward money and help his parents' marriage, too.