Cass Wheeler - a British singer-songwriter, hugely successful since the early 70s, whose sudden disappearance from the music world three decades later has been the subject of intense speculation among her fans - is in the studio that adjoins her home, taking a journey back into her past. Her task is to choose sixteen songs from among the hundreds she has written since her early teens, for a uniquely personal Greatest Hits record, describing the arc of her life through song. It has been over a decade since Cass last put out an album; ten years since a tragedy catapulted her into a breakdown. In the course of this one day - both ordinary and extraordinary - each song Cass plays sets off a chain of memories, leading us deep into her past, and into the creative impulse that has underpinned her work. This is the story of a life - the highs and lows, love and separation, success and failure. Of what it is to live a fulfilled life, and how to make peace with our mistakes.