The fourth and final series of this crime drama airs tonight. If you haven't seen it before it, the show involves six episodes with three cases featuring throughout. The first begins tonight as Chandler, Miles and the team investigate the murder of a man crushed to death by stones. They discover the murder is a 16th century torture and when soon after a second body is found, they come to realise that someone has quite literally started a witch hunt in Whitechapel.