 John accuses Palamides' servant Bernard (Bill Brandon) of murder before Arthur, who grants him three months' grace to prove the accusation or face execution himself.Another knight, Sir Ontzlake (André Morell), takes pity on John and trains him in swordplay so that he can take on an alternative secret identity as the wandering Black Knight.The "Vikings" raid a newly founded monastery and take Lady Linet and its monks to Stonehenge for a pagan sacrifice, but the Black Knight arrives and saves her, closely followed by Arthur and his knights, who defeat the pagans and destroy Stonehenge.