Cas Russell is back — and so is her deadly supermath.

Cas may be an antisocial mercenary who uses her instant calculating skills to mow down enemies, but she’s trying hard to build up a handful of morals. So when she’s hired by an anguished father to rescue his kid from an evil tech conglomerate, it seems like the perfect job to use for ethics practice.

Then she finds her client’s daughter . . . who is a robot.

The researchers who own the ’bot will stop at nothing to get it back, but the kid’s just real enough for Cas to want to protect her — even though she knows she’s risking everything for a collection of metal and wires. But when the case blows up in her face, it plunges Cas into the crossfire of a massive, decades-long corporate espionage war.

Cas knows logically that she isn’t saving a child. She’s stealing a piece of technology, one expensive and high-stakes enough that spiriting it away is going to get innocent people killed. But she has a distraught father on one hand and a robot programmed to act like a distraught daughter on the other, and she’s never been able to sit by when a kid is in trouble — even a fake one.

Screw morals and ethics. All Cas wants to do is save one little girl.