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. But the spirit world is a dark and dangerous place... Little does Arthur realize 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.

In the inky depths of an ancient pool, three soothsayers cast a dark judgment upon the King of Camelot. But despite Merlin's warnings, headstrong Arthur refuses to take the words of the Disir seriously and their fury rains down on Camelot. Only the greatest sacrifice can appease them, and with the kingdom in jeopardy, is it one that Arthur is prepared to make? Faced with the King's uncertainty, Merlin has just one chance to save him from his destiny, but this decision comes at the highest price.