The novel opens in the year 1421. England, though engaged in warfare in France, enjoys peace and prosperity at home, but Scotland is in a state of anarchy. Its king, James I, the caged lion of the title, has been a prisoner in England since boyhood, though the king, Henry V, treats him as a friend. The chief character, Malcolm Stewart, is a timid, sickly, scholarly youth, who feels that the best way to protect his tenants and his sister is to give her in marriage to their soldierly cousin Patrick, and himself become a monk. This is found to be no solution. Lilias is placed in a nunnery, Patrick goes to fight the English in France, and Malcolm enters the service of his royal kinsman, James I.