Missing (2009)

When an autistic teenager is discovered wandering lost at the side of the road, DS MJ Croft assumes he is a missing person. However, she soon realises that it is the boy's mother who has disappeared, and becomes increasingly worried for her safety. DC Jason Doyle and Amy Garnett deal with Jan, a young woman whose fiance has disappeared in what seem like suspiciously fraudulent circumstances. And MJ is shocked when her friend, radio DJ Danny, asks her on air about her sister, Ellen, who went missing over ten years ago.