If you haven't seen the previous episodes, I strongly suggest you do. It explains the bound between the two protagonists. Once again Department Q delivers an emotional and strongly written police adventure. By now it's hard to imagine a movie in these series without the constant switch between past and present. It's an interesting way to uncover the timeline and the motives of each character. It just works really well. Is it the best one in these series? Probably not. But it's still worth your time, even if you haven't seen the previous three films. I hope there will be more of these.