Review: Witnesses (S2 E7&8/8), Saturday 16th December, BBC Four

NB: SPOILERS INSIDE Right, let’s get back into it. This series has been dark – very dark – and also very watchable and hugely intriguing. The last we saw of Sandra Winckler had been taken prisoner by¬†Geir Janssen – the man who had been kidnapping women, murdering their exes and siring their children while they…