D.C. Carter and the Afterline Bureau have uncovered missing children before - but never like this.When a fragment of footage exposes abandoned schools linked by underground passageways, the Bureau launches their most dangerous recovery mission yet. What begins as a search for a handful of stolen lives becomes something far greater: an entire generation of children raised below the city, some traumatized, some eerily calm - and some waiting.Ella, the young survivor once pulled from the walls, hears them calling. Not with words, but memory. And when the Bureau descends beneath the First Waterworks, she becomes the key to a world no one aboveground ever knew existed.Seventy-five children wait in the dark.Some cry for rescue.Some stand like soldiers.All of them want the sky.But buried beneath the last ladder is a man the children call The Architect - a caretaker, captor, prophet, and ghost of every decision made too late. He raised them for survival. Ella leads them toward light. And between dawn and flood, Carter must decide what humanity looks like when the world finally sees what has been growing under its feet.The Tenth Key is a gut-wrenching thriller of recovery, revelation, and choice - a story about the price of protection, the meaning of freedom, and a girl who learns that leadership isn't granted.It's climbed.