Librarian Jayne Thorne enjoys her quiet life of tea and books. That is, until she finds a spell book in the Vanderbilt archives that accidentally gives her access to a magical dimension.

Librarian Sylvia Ashe knows nothing about her past, having grown up without a father and a mother who refused to discuss him. When she stumbles upon a diary that suggests she's descended from magicians, she's skeptical. After all, magicians are special, and she's just an ordinary woman who loves books. She seeks answers from a member of the most prominent family of magicians, but she quickly learns that finding the truth won't be easy, especially when he turns out to be as artless as her, and more compelling and dangerous than books.

Miracle Springs is a place of healing. Strangers flock there hoping the natural hot springs, five-star cuisine, and renowned spa can cure their ills. And, if none of that works, they often find their way to Miracle Books, where, over a fresh-baked scone from the Gingerbread House bakery, they exchange their stories with owner Nora Pennington in return for a carefully chosen book. That's Nora's special talent. But when a visiting businessman reaches out to Nora for guidance, he's found dead on the train tracks before he can keep their appointment.

Karigan G’ladheon, running away from school, is traveling through a deep forest when a galloping horse pounds up to her, its rider impaled by two black-shafted arrows. With his dying breath, he tells her he is a Green Rider, one of the magical messengers of the King. Before he dies, he makes Karigan swear to deliver the message he’s carrying, and gives her his green coat, with the symbolic brooch of his office.

May 20, 2019: Homicide detective Mallory is in Edinburgh to be with her dying grandmother. While out on a jog one evening, Mallory hears a woman in distress. She’s drawn to an alley, where she is attacked and loses consciousness. May 20, 1869: Housemaid Catriona Thomson had been enjoying a half-day off, only to be discovered that night in a lane, where she’d been strangled and left for dead. When Mallory wakes up in Catriona's body in 1869, she must put aside her shock and adjust quickly to the reality.