While Camelot prepares to celebrate peace with Mercia's visiting prince Bayard, Nimueh forges a poisoned chalice and places it at the royal table where Arthur is to have his cup filled by Merlin. Then the sorceress warns the page-magician, blaming Bayard, so king Uther makes Merlin test the drink from the goblet (as he is a 'disposable' servant). Gaius diagnoses a fatal poison; the only cure is from a flower which grows only in certain caves, but the perilous journey to it may take too long. Arthur bravely rides, although Uther forbids him to 'risk a king' for a pawn. Nimueh plays the local damsel in distress and guide, to make sure Arthur is fully exposed to horrible monsters; but even on his deathbed Merlin conjures a magical aid. When Arthur brings the flower, Uther jails his disobedient heir and refuses to have it brought to Gaius, but now, courtier ingenuity helps out endangered magic.