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.

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.

Casey's Unit is, as ever, full of troubled, disaffected pupils, and new arrival Leo is something of a conundrum. Thirteen-year-old Leo isn't a bad lad - in fact he's generally polite and helpful, but he's in danger of permanent exclusion for repeatedly absconding and unauthorised absences. Despite letters being sent home regularly, his mother never turns up for any appointments, and when the school calls home she always seems to have an excuse.

Struggling to cope with three young children, Janie turns to experienced foster carer Cathy Glass. Helping the family each morning, Cathy soon uncovers how dangerous their situation has truly become. Riley and his two little siblings, Jayden and Lola, are not safe at home. With all three children in her care, will Cathy be able to rebuild their lives – and Janie’s?