The Crystal Cave is the story of Merlin’s youth. Merlin is born to Lady Niniane, the daughter of the King of South Wales. His mother is unwed and will not tell anyone who Merlin’s father is. Her father whips her during her pregnancy to try to make her tell him and she will not. Merlin does not play with the other children and is bullied by them. His grandfather does not like him.
When Merlin is six years old, Prince Camlach returns to his home. He has been serving the High King. Camlach does not like Merlin because he fears that his father will come for him and threaten Camlach’s claim to his father’s kingdom. He attempts to kill Merlin, but Merlin can see the poison in the apricot that Camlach gives him. Camlach becomes angry and tells Merlin to keep away from him.
Merlin is given a tutor. The family plans to send him to the Monastery when he is old enough. As he gets older, he begins to skip out on his lessons. He goes up into the hills and meets Galapas. He helps Merlin to understand his Sight and how to use the Crystal Cave. The cave helps enhance his visions. Galapas tells Merlin to accompany his grandfather when he goes to meet with the High King Vortigern. Merlin does not know why he must go along until he finds a cave system under Tomen-y-Mur. He believes this is why Galapas insisted that he go on the trip. Merlin had seen these caves while in the Crystal Cave. The High King is meeting with the King of the South of Wales to ensure that he will be on his side if the High Kings sons try to take his kingdom. They did not like when their father took a Saxon bride and see their only way to secure succession is by force. This is the way that Vortigern took the Kingdom. He killed the High King and took the kingdom. The rightful heirs fled to relatives in Brittany as they were too young to fight.
The King of the South of Wales and Camlach disagree about who to support, if a war should come. Camlach thinks they should support Vortimer because the High King is old and his Queen is hated because she is a Saxon. The High King brings the Saxons to Britain to fight for him thus inviting invaders into their land. While in the Crystal Cave, Merlin sees the death of his grandfather and the death of his slave Cerdic. The King is killed when he slips on oil spilt on the floor when Cerdic is refilling the lamps in the palace. It is an accident, but the guards kill Cerdic for causing the King’s death. Camlach rides back from a hunt to find his father dead. The kingdom is now his. Niniane asks to go to the nunnery to spend the rest of her days. She asks that Merlin go to the monastery. Camlach agrees that she may spend the rest of her days at St. Peters.
Merlin rushes to the palace. He does not go into the main gate, but slips over the stone wall. He knows that Camlach will now want him dead. He finds Cerdic’s dead body in his room. Merlin gathers his belongings and sets Cerdic’s body aflame as is the custom for Saxon’s as Cerdic was born a Saxon. Merlin rushes from the palace as the flames catch. When he jumps over the castle wall, he is abducted by two men and taken to their boat. They are sailing for Brittany. They plan to use him to gain favor with Ambrosius, the true heir to the throne of the High King. He is the brother of the man that Vortigern murdered. Merlin is sick on the voyage across the Narrow Sea. Due to his condition the men leave him locked on the boat while they go to tell Ambrosius who they have brought with them from South Wales. Merlin is able to escape the boat, but not knowing the land he stumbles upon the meeting place of Ambrosius and his men. One of these is Uther, Ambrosius’ younger brother. Uther takes a dislike to Merlin. Under the haze of a vision, he is captured.
Ambrosius takes him to his camp and sees that he is bathed and well fed before questioning him. He is interested in Merlin’s parentage and asks him if his mother ever told him who is father is. He tells him that she did not. He asks Merlin if he got his Sight from his mother. Merlin admits that he did, but she feared the power and let it be. Ambrosius has Merlin sleep in his bedchamber in a curtain off bed that is near the door of the chamber. Cadal, a slave of the Ambrosius, brings Merlin breakfast the next day. He has been assigned to be Merlin’s servant. Merlin is treated more like a prince here than he had been in his grandfather’s house.
Ambrosius is training troops for his invasion of Britain. The camp must remain secret so that Vortigern does not expect the invasion. Ambrosius assigns a tutor to Merlin. His name is Belasius. On a ride through the forest with Cadal, Merlin rides off the road and onto an unknown path. He feels he must take this path. The horses are rushed by a boar and Merlin is dislodged from his horse and sprains his ankle. His horse is lame. Merlin must ride Cadal’s horse with Cadal leading the lame pony. They come upon Belasius’ servant, Ulfin in the woods waiting for his master, but he will not tell them from where. A loud cry is heard and Merlin sends Cadal’s horse racing toward the sound. He finds Belasius as leader of a Druid ceremony. He waits for ceremony to end and then confronts Belasius. These ceremonies are illegal. Merlin’s curiosity makes him want to learn more of the religion. Belasius leads Merlin back to the camp, but leaves him on his own when they hear horses coming toward them. It is Uther returning to the camp. He is not happy to see Merlin and finding Belasius’ robes in Merlin’s saddlebags he believes Merlin a druid. Merlin says that he will explain himself to Ambrosius and not Uther. Uther believes him to be his brother’s lover and does not like him for this. Uther and his men take Merlin with them to answer to Ambrosius.
Uther speaks to Ambrosius first, while Merlin goes to his room to change and finds Cadal there. He had rode back thinking Merlin had gotten frightened and returned there. Merlin tells Ambrosius everything that happened that night. Ambrosius is not surprised that Belasius is a Druid. In Ambrosius chamber, Merlin has a vision of a young man and a young woman on a hillside together. He pieces together that Ambrosius is his father. He met her when he was eighteen and slipped into the country to have a meeting with Gorlois of Cornwall who is loyal to him. Having a price on his head, he had to sneak around the country. He and his two men were attacked and Ambrosius was left for dead. Niniane found him and took him to a cave where he recuperated. They fell in love. Niniane would not leave with him. Her brothers would have pursued and killed Ambrosius. He did not know that Niniane was pregnant and she never sent word to him. In the conversion, Merlin calls Ambrosius the King of all Britain. Britain at present is divided into many kingdoms.
Merlin spends five years in Brittany with his father. The camp gets news from Gorlois from Cornwall. Vortimer tired of trying to get the High King to break with the Saxons and protect his people from them, rises against his father. Camlach sides with him. He claims victory against the Saxon, but is poisoned by one of the Queen’s people. Vortigern retakes the kingdom. He has the Saxons return to Britain. Camlach is killed in one of the battles. For his siding with his son, Vortigern annexes Camlach’s kingdom and takes Camlach’s children. Ambrosius sends Merlin to his home of Maridunum and tells him to go to Galapas to make a base. He will get what information he can from him and send word back to Ambrosius. Merlin and Cadal find Galapas’ cave empty. His belongings have been pulled from the cave and burned. His body is found on the hillside. Merlin believes his only chance now for information is from his mother in St. Peters. He tells the porter at the door that his name is Emrys and that he family to Lady Niniane and would like to see her. The woman comes back to say that she will meet him an hour after moonrise on the river walk. Merlin and Cadal go to the palace to wait and run into Dinias, the illegitimate son of Merlin’s grandfather who bullied him during his childhood. He is dressed like a beggar. Merlin takes Dinias for a drink and once drunk Dinias talks too loud and Merlin is captured by Vortigern’s men. They also take his mother from St. Peter’s to see the High King.
Vortigern questions Lady Niniane about Merlin’s father. They both are scared that he may know that Ambrosius is Merlin’s father and that he can use Merlin as leverage. She tells Vortigern that her son was fathered by a spirit that came to her during the night and once she was pregnant she never saw him again. The High King is satisfied by this story and has Lady Niniane taken to a room to rest so that she can return to St. Peters the next day. Merlin is taken to the building of the King’s fortress that keeps cracking and will not stand. The site is at Tomen-y-Mur. Vortigern’s religious advisors have told him that he can only fix the problem by using the blood of a man with no father with the mortar to make the stones strong. Merlin knows it is the cave system under the foundation that is the problem and divinely leads them to the caves and during a vision tells them what they need to do. He foretells of a war between the red and white dragon and that the red dragon will win. Merlin’s mother becomes ill during her trip back to Maridunum.
Merlin’s predictions of what will happen do occur. Ambrosius hearing of Merlin’s capture sails for Britain and is able to take the Kingdom quickly. The people quickly rally behind him seeing him as the true heir to the throne. He unites Britain and begins building what the Saxons destroyed. During one of the battles, Merlin knows that his mother has died. He informs Ambrosius after the battle. Merlin returns to the cave in Maridunum after Ambrosius is crowned. He feels this is where he should be. On the way, he passes through Stonehenge, which is close to Ambrosius’ birthplace of Amesbury. He is fascinated by the ancient site. It is called the Giants’ Dance.
Ambrosius travels to Amesbury and requests Merlin meet him there. He wants to build his memorial on this site. He wants Merlin to go with Uther and his troops to overthrow King Gilloman in Killare, Ireland who is plotting with Ambrosius’ enemies to invade Britain. He wants Merlin to bring back the King’s stone to place on his grave. Merlin prophesizes that while the King lies under this stone the Kingdom shall not fall. A King will be made whose name will stand as long as the Giants’ Dance stands. Uther and his troops take care of the Irish troops and Merlin is able to acquire the king-stone. On the way back to Amesbury, Merlin knows that Ambrosius is dead. He builds the memorial for his father and Uther is crowned King.
Uther falls in love with Gorlois’ wife, Ygraine. He does not try to hide this even from her husband. Ygraine does not comment on his advances and tries to keep away from him, but she and her husband are in London for the King’s coronation and cannot leave until the King gives them leave. Uther calls Merlin to him and asks him to get Ygraine for him. Merlin speaks to Ygraine and discovers that she loves Uther, but cannot betray her husband and risk her reputation and standing. Merlin devises a plan where Ygraine tells her husband that she is pregnant and wants to return home. She feigns feeling ill. Gorlois leaves the kingdom after the coronation without the King’s permission. Uther is to be affronted by this and send his troops to Cornwall to prepare for battle for this outrage. It is all a diversion to get Gorlois out of Tintagel, his fortress, so that Uther can sleep with Ygraine and become pregnant with Arthur as Merlin has foreseen. Uther goes in the disguise of Gorlois to the back gates of Tintagel and is able to get to Lady Ygraine with the help of her servants. During the night, Gorlois attaches the King’s troops to head off the inevitable and is killed.
Brithael returns to Tintagel to inform Ygraine and finds Merlin there. Merlin kills him and races to get the King away. Uther is angry and believes that Merlin knew Gorlois would die and that he and Ygraine could have waited to conceive a son legitimately. Merlin says that son would not have been Arthur. He refuses to accept the son that is conceived that night. Merlin knows that the baby, Arthur, will be given to him upon his birth so that Uther cannot harm him. The legend is that Merlin cast a spell to make Ygraine think that Uther was her husband so she took him to her bed and a son was conceived. The child was given to Merlin for protection.