JONATHAN JEKYLL has always thought of himself as a perfectly ordinary teenager - if a little on the anxious side. He spends most of his time studying, keeping his head down, and trying to stay out of the way, even as his family moves from state to state like they're on the run. Sure, he has strange gaps in his memory and an unshakeable feeling that parts of his life don't quite add up, but he chalks it up to nerves. Everyone has their quirks, right?

At fifteen, Jonathan's world is turned upside down when he stumbles onto a secret his parents have been keeping from him for almost his whole life. Living in his mind, hidden just out of sight, is another personality: Hieronymus "Heron" Hyde, an alter with his own dreams, his own tastes, and his own memories. Heron's been there for years, slipping in and out of Jonathan's life, navigating social scenes Jonathan never would have dared to enter, and shielding him from the bullying and rejection that have followed him since childhood.

As Jonathan grapples with this revelation, he finds himself at odds with his own mind. Heron is everything Jonathan isn't: bold, reckless, and far more comfortable in his own skin. But Heron isn't just a wild spirit; he's also fiercely loyal, protective, and, to Jonathan's shock, willing to teach Jonathan things about himself he'd never known.