In Sweden, the horrific muder of a young girl in the 1980s took almost 20 years to solve. Other murders (just one of which proved to be linked) and departmental politics obstructred progress; but one thing that 'The Hunt of a Killer', a dramatisation of the police investigation, shows is just how difficult it can be to find the evidence needed to close a case. It's an unmelodramatic reconstruction, and in many ways a depressing one: the killer was a lone actor and societal misfit, whose behaviour was alarming in many respects but which went unchecked while his darkest deeds remained hidden. As at a least a semi-normal person, it's horrifying to see what human beings are capable of if allowed to go far enough wrong.