Uther is determined to wipe out magic in Camelot once and for all, and this time no one is beyond suspicion. He summons the most dreaded witchfinder in the land, Aredian, a terrifying man who will stop at nothing to uncover sorcery. Gaius impresses upon Merlin how much danger he is in but Morgana needs no such warning. She is certain Aredian will see straight through her and she will be burnt at the stake. Can Merlin protect Morgana and Gaius without ending up in the flames himself?

When Merlin discovers the beautiful druid girl Freya trapped in a bounty hunter's cage, he knows he must help her escape. Gaius warns against getting involved, but Merlin refuses to listen, harbouring Freya in the tunnels beneath Camelot. But with the bounty hunter searching for his missing prize and a ferocious magical beast on the loose, Freya cannot stay hidden for long.

Merlin's intense new friendship is tested to the limit, and he is forced to make some heartbreaking decisions as he battles to keep Freya safe.