In the last surviving cities of a ruined world, the concept of "woman" has been forgotten to history. Those unfortunate enough to lack a Y chromosome live as second-class citizens in a world dominated by mascs.
Ember is Y negative. He is scorned, bullied, abused by every masc he encounters, at work and at the gym. Not even his Y negative roommate cuts him any slack. He wants so desperately to be accepted as a masc that he'd rather buy black market testosterone than food. Something's gotta give — he needs a change in his life, but has no idea how to find it.
Jess is a masc with a passion for studying the recovery of their devastated world. His boyfriend is pressuring him for more commitment, and his father expects him to take over the family business. He can't wait to get away from civilization for his seasonal research out in the wild.
When Jess offers Ember a job, their lives collide in the isolated wasteland, and their initial attraction turns into a relationship that horrifies those around them. Soon their struggle to stay together and to be who they are turns into a fight for their lives.