Lochleven

Lochleven Castle is the home of Margaret Erskine, mistress of James, King of Scots. Their son, Lord James Stewart grows up knowing he can never be king, but Margaret is determined nothing shall stand in the way of his ambition. Surviving through the turmoil of the 16th century Scottish Reformation he achieves ultimate power as regent, king in all but name.
But then, unexpectedly, his half-sister, the young Mary, Queen of Scots, is widowed and returns to Scotland determined to rule in her own right. And Margaret, who hated the girl’s mother Marie de Guise for usurping her position, will make sure the young queen’s authority still depends on Lord James, Earl of Moray. Lochleven Castle becomes the prison of the young Queen, and Margaret becomes her jailor.
This is the third in Walkinshaw’s trilogy of novels about the Scottish Reformation. The others are Knox’s Wife and The Five Year Queen.