Kit McCarthy hasn't seen her identical twin sister, Billie, in more than a decade.

The sisters don't see eye to eye, which is understandable, considering Kit's a police officer and Billie followed their violent father into a life of crime.

Kit is no angel. Burnt out by years working in child protection, she has been accused of using excessive force in the arrest of a violent drunk. Kit has just been ordered to take time off work when she gets a frantic message from Billie, telling her she has a young son and that somebody is trying to kill her.

And then Billie disappears.

Determined to find her estranged sister, Kit's only lead comes after visiting their father in prison. Malcolm McCarthy claims Billie married a former United States Marine and has been living with a group of sovereign citizens in the desert country of the New South Wales Riverina.

Kit's journey to find Billie takes her through shuttered towns destroyed by drought, where everybody owns guns, nobody talks to cops, and people get lost for a reason.

Out here a war is brewing between a ruthless bikie gang and a separatist community that is re-engaging with society in the most violent way.

Kit will risk everything to find her sister and the nephew she never knew she had.

But does Billie really want to be saved?