When Mark Shillingford commentates on a race in which his twin sister Clare, an accomplished and successful jockey, comes in third, he can't help but be suspicious. As a professional race-caller, he knows she should have won. Did she lose on purpose? Was the race fixed? Why on earth would she do something so out of character? That night, Mark confronts Clare with his suspicions, but she storms off after an explosive argument. It's the last time Mark sees her alive. Hours later, Clare jumps to her death from the balcony of a London hotel ... or so it seems. Devastated by her death, and almost overcome with guilt, Mark goes in search of answers. What led Clare to take her own life? Or was it not suicide at all ... ?