Tabby lives a transient life with her mum Cate, never sticking in one place long enough to make friends.
Until one day, an accident changes everything. Cate is arrested and Tabby realises her life has been a lie: Cate is not her mother.
As she adjusts to her new life, Tabby finds herself drawn to the ocean - the only place she feels happy - and enrolls at a swimming summer school to help her heal.
But all is not as it seems. She and her new friends are cut off from the outside world and she's plagued by a repeating symbol of interlocking circles that follows her everywhere.
As Tabby begins to learn the truth about what the circles mean, and uncovers the terrible lies she's been told about her past, a final twist awaits her - a secret hidden in her DNA...
