Zero Sum Game (Cas Russell, Bk. 1)

The vector calculus blazing through Cas Russell's head makes her the perfect retriever. She can smash through armed men twice her size and dodge every bullet in a gunfight. Until she discovers someone who can twist people's minds. Someone intent on becoming the world's puppet master.

Cas should run, like she usually does, but for once she's involved.

There's only one problem. . . .

She doesn't know which of her thoughts are her own anymore.