Laura Marlin's two greatest loves in life are detective novels and animals, so she is ecstatic when her uncle agrees to let her keep a horse after they rescue it, crazed with fear, from an overturned horsebox. But he has a condition. Before he will allow her to adopt it they have to find its former owner, just to ensure that it hasn't been stolen. A visit to Newmarket to investigate the thoroughbred's origins leads Laura to the Kentucky Derby in the US and deep into the murky world of race-fixing.