Gavin Hay is devastated when he learns that his parents, who have spent their lives in dangerous service to the King, have disappeared while on a mission.

He sets off to find them, not knowing whether he'll be rescuing or bringing him their bodies—with his fey sister Isobel's whispered parting words echoing in his brain: "Gavin, you must trust only a lass who is marked in scarlet, with hair like a lad..."

He finally arrives at the Menzies Keep, knowing that he must keep his wits about him with these known traitors, or he will be despatched as speedily as his lost parents.

But he finds an unexpected ally: the girl spoken of by his wee sister Isobel. Firtha, a lowly maid in the keep, is treated worse than the curs that scrounge around the muddy yard. But she is brave, and resourceful, and eager to help the son of Lady Hay, who was so kind to her.

But life in the Highlands is not easy, especially for a King's spy. Gavin has to call upon all his strength and cunning to face his enemies and to find out the fate of his parents.

And Firtha? Dare she dream that one day she might be more than a maid to Gavin Hay?