Merlin series 5 episode 4 will air on BBC One on 20 October at 8.25pm to 9.10pm.
When a stranger gives Arthur the power to summon the dead, the king finds himself torn between head and heart.
Unable to resist temptation, he seizes the chance to speak to the person he misses most – his father, Uther Pendragon (Anthony Head). But the spirit world is a dark and dangerous place, for little does Arthur realise that his decision comes at a terrible price. Against all odds, Merlin must put right Arthur’s mistake before Camelot, and everything they have built, is destroyed forever.
Colin Morgan is Merlin, Bradley James is Arthur, Angel Coulby is Gwen, Katie McGrath is Morgana, Richard Wilson is Gaius and John Hurt as the voice of the Great Dragon. Tom Hopper, Rupert Young, Eoin Macken and Adetomiwa Edun returns as The Knights of the Round Table. Special guest star Anthony Head as Uther.