Just when Casey thinks her foster care duties are done, she’s asked to look after Sam, a troubled nine-year-old with a violent streak who drove his previous guardians to release him of their care. It soon unfolds, however, that this is no simple case. Determined to get to the root of Sam’s behaviour, Casey is committed to uncover his mysterious past only to find out something far darker than she ever imagined.

The Watsons are no strangers to sibling placements, but when Casey takes the call from her supervising social worker one frosty January morning, she can instantly tell from the tone of her colleague’s voice that there’s a complicated case ahead. And she’s right. A four-day-old baby boy called Tommy - born in prison - plus his four-year-old half-brother, the lively Seth. A month later, the very moment she gets out of prison, the boys’ mother - a 19-year-old called Jenna - also follows.

Casey Watson is back, doing the job she does best - rolling up her sleeves and fostering the children who, on first meeting, seem like hopeless cases. But when she meets Miller and discovers the truth about his disturbing childhood, even Casey begins to doubt if this child will ever be able to accept love. Found naked and alone on a railway track, Miller was just five when he was first admitted into the care system.

Brought to Casey as a short-term emergency placement, 14-year-old Adrianna arrives with nothing but her gratitude. Having turned herself in to a social services office some 100 miles away, she has no possessions, no English and, apparently, no history - not that she's willing to share, anyway. She is a beautiful young Polish girl, with the bearing of a ballerina, but is terrified, malnourished and unwell.

A 5-year-old boy, Ethan, is brought to Casey in the middle of the night after the sudden death of his young mother after a drug overdose. Estranged from her parents, Ethan’s mum had been abused by her ex-partner, and began taking drugs to cope. Ethan is obviously lost and bewildered, and regularly wakes up screaming for his mum in the night. He begins to lash out at other kids at school and his behaviour becomes more volatile.