In an ancient city carved from stone, one desperate young woman searches for peace—in the calm before the deadly clash of empires.

 In 106 AD, a single mother can be certain of one thing—destitution. So Cassia and her six-year-old son flee to Petra, her late husband's birth city, in hopes of finding refuge in the loving arms of family.

But the great stone city is not what Cassia imagined. And a secret about her husband reveals her son's true bloodline, making the boy the target of a royal conspiracy.

Petra Kronos has a simple, happy life. But it’s never been ordinary. She has a pet tin spider named Astrophil who likes to hide in her snarled hair and give her advice. Her best friend can trap lightning inside a glass sphere. Petra also has a father in faraway Prague who is able to move metal with his mind. He has been commissioned by the prince of Bohemia to build the world’s finest astronomical clock. Petra’s life is forever changed when, one day, her father returns home – blind.