The scene of "A Legend of Montrose" is laid "during the period of that great and bloody Civil War which agitated Britain during the 17th century," and which finally cost Charles I his kingdom and head. In the Scottish Highlands the struggle lay between the Covenanters who adhered to the Royalist cause, and the Presbyterians; the field being further complicated by private feuds and the presence of outlaw clans.

Dugald Dalgetty, a boastful soldier of fortune, meets the Earl of Menteith, who persuades him to join the Royalist army. They remain overnight at Darnlinvaroch Castle, where Dalgetty is told the story of Angus and Allan McAulay and their troubles at the hands of outlaws. Allan, who is of gloomy nature, is soothed by the harp-playing of Annot Lyle, a girl whose birth is enshrouded in mystery. The next day several heads of clans arrive; whereupon the Earl of Montrose, who has been in disguise, takes command of the troops in the King's name ...