Cold Case (2003)

The American network take on the idea, and still the most comforting one. Kathryn Morris plays Detective Lilly Rush of a Philadelphia cold case squad, and the episodes reopen unsolved killings from years or decades back. What makes it stick is the way it stages time: flashbacks are scored with music from the era of the crime, and characters are double cast, so you meet them as they looked then and as they are now. The emotion is laid on thick, and it works. With seven seasons and 156 episodes from 2003 to 2010, it suits anyone who wants a case wrapped up in an hour.