Explorers don’t last long around here.

Humanity fled underground seven hundred years ago. Quin is sixteen, lives a mile beneath the surface, and cannot stop going down tunnels she was told to stay out of. That exact flaw gets her recruited by the Engineers — a secret order with an iron cog tattoo, weekly pay, and three rules. The first rule is that they don’t exist.

Within a month she has blown up a crime boss’s factory, lost an arm, and gained two things she was never supposed to have: a cyber limb that crushes iron, and Trix — a one-foot robot with an illegal mind, a scoreboard of her failings, and no intention of keeping quiet.

Then the earthquakes get worse. And the enemy her people have feared for a century turns out to be human, hiding, and nothing like the monsters in the stories. Someone has been lying to the colonies for a very long time. Someone who would rather let two hundred million people die than admit it.

One catastrophic quake is coming. Everything underground comes down. Two months. And the only ones trying to sound the alarm are a girl with a borrowed arm, a robot who thinks he’s funny, and a thief who wants the arm.

First book of the Subterrania trilogy. Ages 14 and up — this one goes darker than Echo Island.