Summertime 1987, two young girls grow up in a crumbling seafront house in Dublin in a household which revolves around their silent withdrawn father, an eminent judge.
On the cusp of adulthood, Marie, the eldest, takes responsibility for her young sister Grainne, fulfilling a promise she made to her mother before she passed away.
But then, one night at a school dance, something happens which changes the course of all of their lives.