The story takes place during the Earl of Montrose's 1644-5 Highland campaign on behalf of King Charles I against the Covenanters who had sided with the English Parliament in the English Civil War. The main plot concerns a love triangle between Allan M'Aulay, his friend the Earl of Menteith, and Annot Lyle. Annot is a young woman who has been brought up by the M'Aulays since being captured as a girl during a blood feud against the MacEagh clan (also known as the Children of the Mist). M'Aulay and Menteith are both members of Montrose's army. Annot eventually marries Menteith after it is discovered that she has aristocratic blood, and was kidnapped by the MacEaghs as a baby. This leads to the jealous M'Aulay stabbing Menteith and then fleeing Montrose's army. Menteith survives whilst M'Aulay disappears and is rumoured to have been killed by the MacEaghs.