Sanctuary (Zone Cyborgs Book 4)

After his rescue from Omega-Three-Omega's illegal cybernetics facility, cyborg Jason Formosa longs for a simple, quiet way of living on his friends' farm in the Brava System. His idyllic new life is interrupted when his rescuer, the mysterious Cecily Barris, sweeps back into it with devastating news: he has a kill switch implanted in his head. There's only one doctor who can deactivate it, who happens to be on the other side of the galaxy.

Cecily has her own reasons for wanting to see the doctor, too. But they fall by the wayside when she and Jason are attacked and chased through space. 

Their pursuer knows who Cecily is. He knows what Jason is. And he'll stop at nothing to catch them.