The realm faces danger from Viking invaders, prompting “Aguar” (Donald Crisp) to dispatch his son, “Valiant” (Robert Wagner), for protection to England's court with king “Arthur” (Brian Aherne). Upon arrival, he finds himself embroiled in a plot involving a deceptive knight linked to the Norsemen who aims to take him prisoner. The identity of this enigmatic character remains unclear. Simultaneously, he becomes part o…