The illusion of innocence - Jacqueline Jacques

Archie Price, painter and police artist, has to attend a murder trial. The murderer, Fred, is on the same train, a prisoner in the guards' van, and Fred's sister, Polly, is also there, wanting to escape from her criminal brother. Fred's gang are desperate enough to derail the train to recover him. Injured in the horrific crash, Polly and Archie are both taken in by local rich farmers to recover, while Fred hides nearby. Polly is so frightened of her brother, she takes the chance to swap identities with another passenger.