In the winter of 1907, an isolated lighthouse off the storm-battered coast of Nova Scotia becomes a cage of shadows and secrets. Dr Zelda Brooks, a brilliant Halifax physician striving to rebuild her reputation after exposing systemic corruption, is summoned to Greyhaven Light to attend to ruthless shipping magnate Gideon Voss. Despised for his cruelty and greed, Voss narrowly survives an apparent poisoning—only to be found dead hours later in the sealed lantern room, murdered beneath the blinding sweep of the revolving lens. Trapped by a violent Atlantic gale, Zelda faces a tight circle of suspects, each harbouring bitter grievances, forged manifests, and desperate motives to silence Voss. But Greyhaven itself proves a treacherous adversary: labyrinthine sea caves, failing machinery, and severed wireless lines actively conceal the clues of a far-reaching, lethal conspiracy born of maritime disaster. Joined by Elias Shaw, the lighthouse’s taciturn, fiercely capable keeper, Zelda enters a perilous alliance where mutual wariness ignites into intoxicating passion. As the storm intensifies, Zelda and Elias must decipher a trail of false signals and unmask a calculated killer before the beacon goes dark—and the tide washes away every surviving witness.