The immortal identical twins, Sara and Sammy, survive in different centuries by using their supernatural paradise, Nysa, to coexist.

The brutalities of their parallel realities make them ruthless killers.

Despite Sammy's heroics, guilt sends her to an asylum, where her once-privileged life soon deteriorates into an endless nightmare. She hides within herself by fading into a vegetative state.

Sara's life also descends into chaos. Her beloved sister dies while giving birth to a stillborn. She is utterly alone until a kind stranger takes her in and tries to help her assimilate. But Sara is too impulsive and doesn't fit the population's norms of the harsh western town. Armed with a six-shooter and a chip on her shoulder the size of Oklahoma, she quickly becomes a wanted fugitive and racks up an impressive number of kills.

Can Sara's ferocious nature help return Sammy to self-awareness?