5. Mayday (BBC, 2013)
While the whole country seemed to fall in love with ITV's mystery Broadchurch, this BBC 5-parter went comparatively under the radar. It was broadcast over consecutive nights the week Broadchurch started, and was, in fact, a much better show. It focuses on the disappearance of Hattie from a village during Mayday celebrations. Several shady characters present themselves as potential suspects over the five episodes, most plausibly Everett (Aidan Gillen), the initially repulsive Irish father struggling to recover from a broken marriage, and Malcolm (Peter Firth), a successful businessman with some very dark secrets. There's an intriguing ensemble of other characters too, each one with their own set of demons that links them with Hattie's disappearance. The final reveal is as good as any I've seen, the final shot lingering in the mind long after the credits have rolled.