Mole Steve Coogan’s underground home is crushed when the meadow above is wrecked by a steam shovel driven by the Weasels. The Water Rat Eric Idle helps Mole reach Mr. Toad Terry Jones, who invites them to join his flashy new horse-drawn caravan. A loud, chaotic turn of luck follows when a motor car frightens the horse and sends the caravan tumbling, and Toad quickly becomes infatuated with speed and engines. He funds his obsession with loans from the Weasels, and their vindictive Chief Antony Sher pressures him to sell Toad Hall, weaving danger into Toad’s reckless fascination with driving.
After a tense encounter with the Weasels in the Wild Wood, Toad, Rat, and Mole seek refuge in Badger Nicol Williamson’s underground lair. Badger, a steady moral compass, tries to curb Toad’s car-obsessed impulses, but Toad stubbornly refuses to listen and soon finds himself arrested for stealing and crashing a motor-car outside a pub. During the trial, the Chief Weasel poses as a rabbit and manipulates the Jury to secure a guilty verdict. Toad’s rage erupts in court, and the Judge Stephen Fry sentences him to a 100-year confinement in a castle dungeon.
Back at Toad Hall, Rat and Mole are evicted as the Weasels take over. They tunnel beneath the castle to free Toad, aided by the jailer’s daughter Julia Sawalha and her sardonic tea lady aunt Victoria Wood. The trio then boards Engine No. 592, with the engine driver Bernard Hill helping them ride on the footplate. Police, who have secretly boarded the carriages behind the engine, wave furiously to stop the train, while the driver tries to intervene. In the chaos, Toad pleads for help, and the sympathetic driver agrees to assist as the police attempt to halt the locomotive, culminating in a derailment that leaves Toad, Rat, and Mole separated by the wreckage and danger.
The Weasels’ full scheme comes to light: they’ve constructed a dog-food factory over Mole’s former home and plan to blow up Toad Hall to replace it with a slaughterhouse, aiming to spread their control over Riverbank. They have also damaged the area around Badger’s residence, spurring Badger into a vengeful stance. Badger and Rat attempt to infiltrate Toad Hall disguised as Weasels, but they are discovered. Toad, Badger, and Rat face peril on a dangerous mincing machine the Weasels intend to use for their sinister plan. The clock ticks as Mole breaks in and disables the machine, freeing them from immediate danger.
In a premature bid for victory, Clarence Weasel and Geoffrey Weasel clash over leadership, while the others drunkenly pick sides. The distraction buys the protagonists time to raid the Weasels’ stronghold, incapacitating most of the gang. The Chief survives the coup attempt, and Toad races to stop him from reaching the factory where a detonator supposedly lies. Unbeknownst to them, Rat and Mole had swapped the labels, leading the Weasels to believe the explosives are merely bone supplies for the factory. In a furious explosion, the Chief blows himself up along with the factory, leaving Toad Hall intact and his friends alive.
In the aftermath, Toad delivers a public vow to abandon motorcars and grow more mature, while Mole’s home is finally repaired. Yet the ending hints that Toad’s wanderlust remains; he is seen speaking with an airplane salesman, suggesting a new craze. The crowd watches as Toad flies above, and a disappointed Badger swears never to help him again. The end credits reveal Toad continuing to roam the skies, charting a wild new horizon for his restless spirit.
