Marlowe and Harper share a bond deeper than most sisters, shaped by the loss of their mother in childhood. Harper has Down Syndrome and a congenital heart disorder. Now 25, Marlowe is finally living her own life abroad, pursuing her studies of a rare species of butterfly secure in the knowledge Harper's happiness is complete, having found love with boyfriend, Louis. But then she receives the devastating call that Harper's heart is failing. She needs a heart transplant but is denied one by the medical establishment because she is living with a disability. Marlowe rushes to her childhood home in Hong Kong to be by Harper's side and soon has to answer the question - what lengths would you go to save your sister?