Null set
(Book)

"A Tom Doherty Associates book."

Sequel to: Zero sum game.

"Cas Russel has decided to Fight Crime". She definitely doesn't have a cape, and she's working on the whole morals issue, but she does have a real-life superpower: with her extraordinary mathematical ability, she can disarm bombs or outshoot an army. But Cas's own power also has a history, one she can't remember - or control. One that's creeping into her mind and fracturing her sanity... just when she's gotten herself on the hit list of every crime lord on the West Coast. And in the crosshairs of her best, only, sociopathic friend. Forget saving the world - Cas may not even be able to save herself."--Publisher description.