The protagonist and narrator is Merlin, who supervises the birth and raising of King Arthur. (In this version, Merlin's father is Aurelius Ambrosius, so he is Arthur's cousin.) The Duchess Ygraine is said to have conspired with him to herself bear Arthur to Uther Pendragon; whereafter Merlin goes into hiding, to evade accusations, and learns that Uther wishes the child to be hidden, until another (legitimate) son is born.
In later chapters, Merlin gives the child to his own nurse Moravik, who later sends him to Count Ector of Galava to be trained in courtesy and warfare. Thereafter Merlin visits Constantinople, where he learns from his relative Adhjan that Magnus Maximus (alias 'Macsen Wledig') possessed an especially beautiful and well-made sword, which was taken back to Britain after his death.
Inspired by a dream which he believes prophetic, Merlin finds the sword in a deserted temple of Mithras. There, Merlin becomes a hermit in an obscure shrine, providing healing to the injured and advice to the insecure. Later, Merlin becomes Arthur's tutor and that of two other boys: Arthur's foster-brother Cei and his friend Bedwyr.
One day, Arthur discovers the sword of Maximus— his ancestor and Merlin's — hidden in a cave on an island in the centre of a lake, and names it Caliburn. Later he wins his first battle in a decisive victory against invading Saxons; whereupon his parentage is revealed and he is proclaimed the heir to Uther Pendragon. Shortly before he learnshis identity, he mistakenly commits incest with his half-sister Morgause, and thus sires Mordred. When challenged to prove his birthright, he reveals Caliburn to the assembled kings.