A heart-wrenching story about a lighthouse keeper's wife who struggles to protect her family at the edge of the known world.

Life is hard in Ireland in 1867. Eliza Carthy moves with her lighthouse-keeper husband James and sons Peter and Joseph to the remote island of Skellig Michael. Eliza is proud of her husband and his promotion to Principal Keeper and is eager to support him in his work and fulfil her duty as a good wife and mother. But life in this extreme location is challenging.

The island is 54 acres of jagged rock, jutting out of the Atlantic, with no way of communicating from or leaving the island. The keepers must rely on a tender boat to deliver news, supplies and act as their conduit to life on the mainland. The island is exposed to extreme changes of weather and the landscape is fraught with danger.

When assistant keeper Edmund and his wife Ruth arrive, Eliza hopes for respite. But her new neighbours are not what she'd expected. They blow hot and cold, seemingly wanting Eliza and family to leave Skellig Michael, making her question her sanity.

Will Eliza be able to keep her family safe at the edge of the world? And can her marriage survive all that the island throws at them?