Deadly. Mercenary. Superhuman. Not your ordinary math geek.

Cas Russell is good at math. Scary good.The vector calculus blazing through her head lets her smash through armed mentwice her size and dodge every bullet in a gunfight. She can take any job forthe right price and shoot anyone who gets in her way.As far as she knows, she’s the only person around with a superpower… butthen Cas discovers someone with a power even more dangerous than her own.Someone who can reach directly into people’s minds and twist their brains intoMoebius strips. Someone intent on becoming the world’s puppet master.Someone who’s already warped Cas’s thoughts once before, with her none thewiser.Cas should run. Going up against a psychic with a god complex isn’t exactly arational move, and saving the world from a power-hungry telepath isn’t herresponsibility. But she isn’t about to let anyone get away with violating herbrain — and besides, she’s got a small arsenal and some deadly mathematics onher side. There’s only one problem…She doesn’t know which of her thoughts are her own anymore.