When Merlin agrees to help a young Druid boy, he has no choice but to leave Camelot on a dangerous mission. And with the citadel distracted by the visit of the fearsome Sarrum of Amata, it seems that no one will notice his absence.

Cast: John Hurt, Alfie Stewart, Rupert Young, Angel Coulby, Bradley James, Colin Morgan, Richard Wilson, Katie McGrath, John Shrapnel, Eoin Macken, Tom Hopper, Alexander Vlahos, Matthew Clancy, Mitch Benn