The city of Avalon is under the grip of a terrible dragon that the priests try to fight. But under the features of this dragon hides in reality Brendan, the victim of a curse. Only Blaise is aware of and perhaps will reveal the truth in the open. For his part, Ahès, whose power continues to grow, persuades Merlin to change politics and attack as a priority, Avalon. But in their ranks, Erwan the Druid and the God Nuada disapprove of this will. Very quickly, Erwan is put to death by the goddess and Nuada is "invited" to face Merlin in duel. The fate of Avalon depends on it.