When three children wander into an abandoned coastal manor, they think they're chasing a story. What they find is a secret that refuses to stay buried.

After their father leaves on a long business contract, siblings Kate and Ben are sent to live with their aunt in the quiet seaside town of Windmere. The cliffs are steep, the air smells of salt and iron, and the locals avoid talking about the house that sits above the tide - Greywater House, locked and empty for fifteen years.

Everyone says the place is haunted, but the truth is far worse.

When Kate and Ben meet Spider, a sharp-eyed boy who knows every forgotten path below the cliffs, the three decide to explore the ruins. What begins as a summer adventure turns into something darker when they discover the house is not abandoned at all. Inside lives Miss Markham, the estate's last heir, with her new caretaker and his two men - Wilberforce, Morris, and Stakovich. They warn the children to stay away, but by then it's already too late.

Because beneath the house lies a cellar that has never been opened, and something inside it is waiting to be found.

As the children dig deeper, they uncover a trail of lies, stolen lives, and the remains of a crime that refuses to fade. Miss Markham's past unravels, Wilberforce's intentions twist into violence, and the cellar's silence grows louder each night. Soon Kate and her friends must choose whether to flee, or to face what lives in the dark - not knowing if it is human at all.

Years later, the sea has claimed everything. Only echoes remain - whispers under the tide, reflections that do not match, and a rhythm in the water that still sounds like breathing.

The Locked Cellar is a slow-burning psychological horror novel that blends mystery, dread, and emotional realism. Set in a decaying coastal town, it explores what happens when memory becomes a trap, when truth and imagination collide, and when the sea itself begins to remember.

Fans of The Haunting of Hill House, Sharp Objects, and The Others will be drawn into Marion Keane's unsettling debut - a chilling portrait of guilt, loyalty, and the things we bury to survive.