The Mole abandons his spring cleaning to frolic across the meadow, where he sees the river for the first time. There, he meets the Water Rat, and the two have a picnic as the Water Rat describes the lives and personalities of the Badger, the Otter, and the Toad. On the way back, the Mole tries to row the boat but overturns it. The Water Rat drags them and their belongings to his den, where they stay. Soon, the Mole and the Water Rat visit the Toad, who is delighted to see them. He shows them his new caravan and says that he intends to travel across the countryside. They agree to join him, but by nightfall, they are tired from doing most of the work while the Toad rides in style. The next day, a motor car speeds by, overturning the caravan. The Water Rat and the Mole pack up and return home along with the Toad, who is lost in the fantasy of having a motor car. 

After the Water Rat refuses to visit the Badger, the Mole sneaks out to do so by himself. He quickly becomes lost and afraid in the Wild Wood. The Water Rat wakes up to find the Mole missing and sets out to rescue him. Reunited, the two try to return home, but snow begins falling, and the Mole trips on what turns out to be a door knocker. After some digging, they find the Badger’s front door. The Badger welcomes them into a warm, cozy kitchen and asks them about the Toad, who has wrecked six motor cars, been hospitalized three times, and accrued numerous fines. They vow to set him straight, then go to bed. The next morning, they eat breakfast with two lost hedgehogs and the Otter. The Badger gives the Mole a tour of his den. He then returns the Mole and the Water Rat safely to the edge of the Wild Wood. 

On their way home, the Water Rat and the Mole pass through a village and spy on its domestic scenes. Along the road, the Mole picks up the scent of his home, and he feels a passionate longing. The Water Rat hurries him along, but when the Mole begins to cry, the Water Rat agrees to visit the Mole’s home. He admires every part of the Mole’s home and dismisses all of the Mole’s objections about his things being shabby, dirty, or insufficient. Field mice sing them Christmas carols, and the two host a fine party for them before going to bed. 

One morning, the Badger reminds the Water Rat and the Mole of their promise to cure the Toad of his reckless driving obsession. Together, they enter his manor house, strip him of his driving clothes, and lecture him. When the Toad refuses to apologize, they lock him in his room and take turns keeping watch. The Toad pretends to be sick to escape from the Water Rat. Then, he walks to a nearby village, and has dinner at an inn. While there, the Toad steals another guest’s motor car and is arrested. He is tried for theft, reckless driving, and being disrespectful to the police, and is sentenced to twenty years in jail. While the Toad is in jail, the Otter’s young son Portly gets lost. The Mole and Water Rat travel the river until dawn, when they hear faint music. They follow it to find a demi-god of nature who is playing the pan pipes. The Piper cradles Portly at his feet. The Water Rat and Mole bow and the Piper disappears, causing them to forget what they saw.  

Back in jail, the Toad rebukes himself for being so foolish. The jailer’s daughter takes pity on him, and, with the help of her aunt, a washerwoman, the Toad escapes, wearing the aunt’s clothing as a disguise. Having left his wallet behind, the Toad begs a train ride from an engine driver, who helps him escape the police. Meanwhile, back by the river, fall is setting in, and the Water Rat resents that his companions are heading south. He begins to feel restless himself after a Sea Rat enchants him with tales of life in various port towns. In a trance-like state, the Water Rat packs up to leave before being rescued by the Mole, who reminds him of his simple domestic comforts. 

The next day, the Toad continues his journey back to Toad Hall. Still in disguise as a washerwoman, he hitches a ride on a canal barge. But soon, he insults the barge woman, causing her to fling him into the water. In retaliation, he steals her horse, which he sells to a gypsy. He then gets a ride in a motor car with the very people whose car he stole. Thinking he’s a washerwoman, they find it amusing that he wants to drive, so they let him. Unable to control himself, the Toad wrecks their car and they chase him. The Toad falls into the river and is swept downstream, where the Water Rat rescues him. 

The Toad learns that the weasels, ferrets, and stoats of the Wild Wood have overrun his estate. After a few unsuccessful tries to get into Toad Hall, the Toad agrees to the battle plan organized by the Mole, the Badger, and the Water Rat. The Badger knows of a secret underground entrance they can use to ambush the weasels. Before launching their attack, the Mole uses the washerwoman’s outfit to sow distrust between the stoats and the weasels. Using the Water Rat’s weapons, they retake the Toad’s property. After their victory, the Badger insists that the Toad throw them a banquet. The Toad plans to use the occasion to sing his own praises, but his friends force him to remain humble as they celebrate their shared victory.