The police discover that Rachel was once the nanny for a couple whose baby son,Joe, also died and Walker wants to exhume the child's body. Whilst the mother, Gina, is eventually cooperative, her husband Lee is dead against the idea and is actually defensive of Rachel, hardly surprising as he had had an affair with her. To complicate matters, Poppy's mother Suzy, is revealed to be in fragile mental health and could also be guilty of killing her child. (thetvdb.com)