Detective Vincent Ruiz has no memory of how he ended up in the Thames with a bullet in his leg, or where the photo of a kidnapped seven-year- old girl came from that was found in his pocket. After a bloody boat is discovered nearby, it's clear that Ruiz was not the only casualty. Under investigation by his colleagues and accused of faking amnesia, Ruiz turns to Joe O'Loughlin, hoping the psychologist can help unlock his memory.