Barrie has lived a sheltered, joyless life at Hillard House under the watchful eye of her puritanical grandmother, Mrs. MacDonald. Her only escape is the forbidden garret, where she secretly discovers the discarded belongings and portrait of her mother, Barbara Ballantree, an actress who supposedly caused her father's death. Emboldened by this revelation, Barrie flees into the night, carrying only a family heirloom and a fierce desire for truth.
At the Carlisle railway station, she encounters Ian Somerled, a wealthy and enigmatic Scottish-born artist. Mistakenly believing her to be a runaway with a marketable antique, he steps in as her protector, refusing to let her wander alone. Rather than returning her to her grandmother, Somerled invites Barrie to travel with him and his literary acquaintances through the romantic borderlands of Scotland towards Edinburgh, where her mother is currently performing.
As they traverse historical sites from Carlisle Castle to Gretna Green and the Galloway moors, Barrie is intoxicated by the beauty of her homeland and the magnetic presence of her companion. She learns of Somerled's own past as a poor crofter's son who fled Scotland after a bitter insult from her family's lineage, only to build an empire of art and wealth in America. Their journey is marked by unspoken feelings, shared wonder for Scottish history, and a growing intimacy that blurs the lines of protection and romance. When they finally reach the edge of their destination, Barrie must face the reality of meeting her long-lost mother, even as she realizes that the road with Somerled has forever altered her perception of the world and her place within it.