The novel, narrated by Englishman J., tells of a boat trip along the Thames, with his friends George and William Samuel Harris. The three, together with the dog Montmorency, travel for days, they cross the English countryside and live unexpected and amusing adventures. The trip is dotted with a series of comic gags on the joys and pains of life on the boat, combined with funny digressions that invent stories in their own right, in the best style of English humor. All this seasoned with realistic descriptions of the regions crossed by the three friends and brief notations of philosophy for the non-professionals.