The novel follows the adventures of Mole, Rat (Ratty), Mr. Toad, and Badger, four anthropomorphic animals living near a river in the English countryside.

Mole, tired of his underground home, ventures out and meets Rat, who introduces him to the joys of the river. They become close friends, spending time boating and enjoying the peaceful countryside.

They visit Toad of Toad Hall, a wealthy but reckless toad who becomes obsessed with motorcars. His obsession leads to reckless driving, accidents, and financial ruin. Despite his friends' warnings, he continues his reckless behavior and is eventually arrested for stealing a car.

Meanwhile, Mole and Rat have their own small adventures, including an encounter with Badger, a wise and reclusive figure who takes them in during a snowstorm. Badger later joins them in an effort to help Toad reform.

Toad escapes from prison using disguises and tricks, eventually returning home only to find that his grand estate, Toad Hall, has been taken over by weasels and stoats from the Wild Wood.

With the help of Badger, Rat, and Mole, Toad leads an attack to reclaim Toad Hall. They succeed, and Toad, now humbled by his experiences, becomes a better friend.

Friendship and Loyalty - The characters support each other despite their flaws.

The Beauty of Nature - The novel celebrates the joys of simple country life.

Adventure vs. Responsibility - Toad's reckless nature contrasts with the wisdom of his friends.