When Rory, a young and inexperienced keeper, arrives for his shift at the isolated lighthouse, he finds himself under the wary watch of two seasoned men-Arthur, who longs for the family he left behind, and Charles, whose tragic past has turned him into a brooding recluse. Their duty is simple: keep the light burning. But the Flannan Isles are a place where isolation warps the mind, where the sea whispers secrets, and where routine is the only thing standing between sanity and madness.