For fans of Starling House and A Discovery of Witches with a Thomas Crown Affair twist: a contemporary New England coven hides the mysteries that lurk in the marshes north of Boston--and how they are connected to the largest unsolved art heist in modern history. Once, Maeve Ryan was the strongest witch of her generation. But Maeve messed up a spell to contact the Lady of the Fens, an eerie Revenant who lures the unwary to their deaths in the brackish marshlands of the North Shore. Maeve destroyed her reputation, hurt her best friend Ash, and tainted herself with unbound, wild magic that transforms witches into insane Revenants. With unbound power eating away at Maeve's mind, all she wants is to get rid of her magic. Forever. But Ash's research into how the spell went awry leads in an unexpected direction: the Isabella Stewart Gardner Museum, and a link between the Lady and a decades-old art theft worth $500 million. When Ash disappears through a stolen painting's empty frame, Maeve has to follow.

Inside is the Other Marsh, a haunting, deadly realm where only the Lady's rules apply. Within this half-world lie secrets about North Shore's history, Maeve's failure, and the fate of the masterpieces that disappeared over three decades ago. But as Maeve fights toward the truth, she risks her friendship, her coven, and her life against enemies hiding in plain sight.