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.

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.

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?

Harley, 13, has been sectioned under the mental health act after attempting suicide. She was spotted climbing the railings on a footbridge that crossed a busy motorway and pulled to safety by a member of the public. After six weeks in hospital, social services are looking for a short-term placement so she can be kept safe while family therapy takes place. Harley has a family - a widowed mother and an older sister, Milly, who left home with her long-term boyfriend just over a year ago.

Damian is just seven when he is taken in by foster carer Cathy Glass. His mother, Rachel, loves her three young children dearly, but she is vulnerable, naïve and unable to cope on her own. Cathy sets about helping Damian overcome his eating issues, with the hope that he will eventually return home. But when Rachel’s new boyfriend, Troy, arrives on the scene, Cathy becomes deeply concerned. She soon realises that Damian and his siblings are in great danger.