The book is set in the 18th century in the Badgworthy Water region of Exmoor in Devon and Somerset, England.

John (in West Country dialect, pronounced "Jan") Ridd is the son of a respectable farmer who was murdered in cold blood by one of the notorious Doone clan, a once noble family, now outlaws, in the isolated Doone Valley.

Battling his desire for revenge, John also grows into a respectable farmer and takes good care of his mother and two sisters.

He falls hopelessly in love with Lorna, a girl he meets by accident, who turns out to be not only (apparently) the granddaughter of Sir Ensor Doone (lord of the Doones), but destined to marry (against her will) the impetuous, menacing, and now jealous heir of the Doone Valley, Carver Doone.

Carver will let nothing get in the way of his marriage to Lorna, which he plans to force upon her once Sir Ensor dies and he comes into his inheritance.