Green River Rising by Tim Willocks
After three years' hard time, minding no-one's business but his own, Ray Klein wins his parole and chances his hand at a romance with prison psychiatrist Juliette Devlin. That same day, tribal war erupts and the prison - and its infirmary - falls into the hands of its inmates. Klein must choose either to claim his freedom and leave the ones he cares for to die, or risk everything and fight...