Every two minutes someone is reported missing in the UK. Most return, but some do not. The police are unable to investigate every case fully, and so too often these people disappear from memory. But the missing always leave behind traces – clues to who they might have been and where they might have gone.

Dave Grimstead, a retired Detective Inspector, has built an eclectic team of passionate volunteers who follow these clues wherever they lead in the hunt for answers, closure and the truth. Someone Must Know is their extraordinary story. Through ten fascinating cold cases, ranging from bodies discovered at sea to individuals who slipped through the cracks of everyday life, Someone Must Know explores the reality of what it means to search for those who are lost, to reconstruct whole lives from fragments of evidence, and to follow the stories of people who are gone but do not deserve to be forgotten.