At the start of the book, it is spring time, the weather is fine, and good-natured Mole loses patience with his spring cleaning and dares to leave his underground home, heading up to take in the air. He ends up at the river, which he has never seen before. Here he meets Ratty (a water rat), who spends all his days in and around the river. Rat takes Mole for a ride in his rowing boat. They get along well and the two of them spend many more days on the river, with Rat teaching Mole the ways of the river.
What happens next? It's not all smooth sailing in this fabulous story!...