June and Jennifer Gibbons are twins from the only Black family in a small town in Wales in the 1970s and '80s. Feeling isolated from the community, the pair turn inward and reject communication with everyone but each other, retreating into their own fantasy world of inspiration and adolescent desires. After a spree of vandalism, the girls are sentenced to Broadmoor, an infamous psychiatric hospital, where they face the choice to separate and survive or die together.

Heather bumps into Carla, having not spoken to her in years, and presents her with a very unexpected proposition that could change both of their lives forever.