Gwyna becomes a servant to the great bard, Myrddin, and joins King Arthur as he travels across Britain to fight battles against the Saxons and win allegiances from squabbling Lords and Chieftains. Gwyna is a young girl whose village has been burned by King Arthur. She herself is almost caught by the King and his men, but she jumps into the river and swims far away underwater to escape. She is pulled out of the river by a bard named Myrddin. Myrddin explains that King Arthur sacked her village because her master, Lord Ban, did not join forces with the King. In retaliation, Arthur had to forcefully take Ban's holdings for himself. Gwyna finds out, to her dismay, that Myrddin works for Arthur. But Myrddin assures her that she is perfectly safe. He explains that he plans on helping Arthur to unite all the lords of Britain through strong leadership so that they can drive away the Saxons invasion and achieve peace throughout the lands. He thinks that Gwyna may be able to help him and decides to take her as his servant.
Myrddin asks Gwyna to help him convince a superstitious lord to willingly welcome Arthur as his leader by sending the lord a “sign” from the old gods. Since Gwyna can stay underwater for an unnaturally long time, Myrddin asks her to wait under a lake and at his cue, rise from the lake to bestow a golden sword called Caliburn to Arthur. This will convince the lord that Arthur is chosen by the old gods to lead. Gwyna does as she is bid and the whole orchestrated affair successfully convinces the lord to join forces with Arthur.
Later, Myrddin asks Gwyna to dress as a boy and call herself Gwyn as she must hide her identity in case someone figures out she was the "lake spirit". Gwyn becomes accustomed to life as a boy. She follows Arthur and Myrddin as they travel the British countryside gathering allegiance from the people. Gwyn makes friends with another boy named Bedwyr who is related to Arthur. Bedwyr boasts that his older brother Medrawt will one day lead Arthur's war band. As the weeks pass, Gwyna becomes more impressed by Myrddin's bardic skills as everywhere he goes, people seem to believe the stories he weaves. He loves to weave in Old and New gods to give his stories a mystical flair and convince people that Arthur is blessed to lead them to victory and peace. Myrddin paints Arthur as a hero but Gwyna knows the truth.
A year passes and one day, Arthur's band arrive at a seaside settlement headed by a self-proclaimed Saint who calls himself Saint Porroc. The Saint tells Arthur he has no gold for him. Arthur asks only for some shelter and food. The next day, while Arthur and his men have gone off hunting, Gwyna takes it upon herself to investigate the verity of Saint Porroc's story. Gwyna befriends a girl in the settlement called Peri and the two pull a prank on Porroc by making him think God knows he is robbing the poor of their treasures. They search Porroc's hideout and find all the gold plates he has taken from others. Gwyna asks Peri to take off her dress and use it as a bag to carry away the treasure. She finds out that Peri is actually a boy and she understands that Peri's mother was desperate to keep Peri from being recruited as a soldier.
Arthur and his band arrive at a town called Aquae Sulis. He is greeted by the Chief Magistrate who informs him that the Saxons are at their borders. Arthur and his men ride to battle the Saxon troops. Since Myrddin is keeping himself out of the battle, Gwyna also doesn't participate in the battle, though she fears for Bedwyr's life. The battle is easily won, to everyone's relief and the story of the battle's success spreads like wildfire across Britain. Arthur decides to make Aquae Sulis the capital of his reign since it is a wealthy town. Myrddin suggests he marries Gwenhwyfar, the lady of Aquae Sulis, to solidify his power and unite Britain.
After Arthur and Gwenhwyfar marry, Myrddin and Gwyna leave Aquae Sulis to go on their own journey. Gwyna grows up into a young woman and Myrddin knows she can't pretend to be a boy anymore. He asks her to become Gwenhwyfar's serving woman and act like a spy in her household. Gwyna is scared because she doesn't know how to behave like a girl but she will try.
Back in Aquae Sulis, Gwyna grows to like her new mistress, Gwenhwyfar. One day, Peri arrives at Aquae Sulis, wanting to join Arthur's war band. Peri has become Peredur because he can no longer hide the fact that he's really a girl. During a Saxon raid, Peredur is overtaken by a soldier and Gwyna rescues him by pulling his culprit into the water.
During that same battle, Bedwyr is also pulled down and severely injured. Because of his injuries, he can never walk again. Over the next few months, he is nursed back to health and he tries to re-learn how to walk. Gwenhwyfar and his brother Merdrawt work with him, determined that he should walk. Gwenhwyfar requests that Bedwyr become her personal guard and Arthur agrees. Soon, it becomes obvious to Gwyna that Gwenhwyfar and Bedwyr are in love. Gwyna is worried about this foolish romance as Arthur will kill Bedwyr if he finds out. She tells Myrddin, thinking that bard can do something to warn Bedwyr but instead Myrddin tells Arthur. Arthur beheads Bedwyr and Gwyna, distraught, helps Gwenhwyfar escape. During the night, however, Gwenhwyfar disappears and likely kills herself by drowning in a lake.
Gwyna rejoins Myrddin in time to hear that Priests are spreading rumors that Arthur sacrificed Bedwyr to his pagan gods. Gwyna doesn't know what to do as she is sure that if Arthur finds her he will order her death, as well. She finds out from Myrddin that Cei, one of Arthur's loyal men, has taken a band of soldiers to go off to a battle, far from Aquae Sulis. Among the soldiers is Peredur. Worried about Peredur's safety (because he's not a very good soldier), Gwyna disguises herself as a boy again and joins them. At first, Peredur avoids, Gwyna, however, likely because he's embarrassed of what Gwyna knows about him. But, when Gwyna jokes with him about the time they tricked Porroc, Peredur opens up again and they become friends.
One night, Cei's soldiers are ambushed by Irishmen who kill Cei. Gwyn and Peredur escape alive but Peredur is injured and becomes feverish. Gwyn decides to convince Peredur to continue to live by pretending to be an otherworldly being come with a special elixir for him. Peredur doesn't know she is a girl so she appears to him, naked and bearing a wooden cup full of lake water which she makes him drink. Peredur is mesmerized. After drinking it, he is filled with new energy and his condition stabilizes.
As Peredur and Gwyna travel, they hear news about what's happening to Arthur. Apparently Bedwyr's brother, Medrawt has gathered an army to fight against Arthur as vengeance for Bedwyr's death. Meanwhile, Gwyna learns that after she ran off with Peredur, Myrddin became sick. Gwyna rushes back to Aquae Sulis to tend to Myrddin. Myrddin passes away, after telling her how he always thought of her as both his own son and his own daughter. Soon after, Arthur comes looking for Myrddin. Gwyna tells him that Myrddin is dead.
Gwyna puts on Myrddin's old cloak and, from a distance, Arthur thinks Myrddin is alive. Dressed as Myrddin, Gwyna witnesses Arthur being felled in a battle. Upon rushing to hear his last words, he asks that she throw Caliburn back into the lake.
The story ends with Gwyna traveling the country, telling stories about Myrddin and Arthur.
Best part of story, including ending:
I thought it was interesting that Myrddin a.k.a. Merlin was described as a regular man who was just a bard that was very adept at creating illusions and spreading heroic stories.
Best scene in story:
My favorite scene was when Peredur arrives at Aquae Sulis to join King Arthur's war band. Because Peredur thought he was a girl for most of his life, he knows nothing about how to behave like a boy. He enters Aquae Sulis comically, wearing a pot on his head, a moth-eaten cloak and riding a nag. It was just a funny and slightly pathetic scene.
Opinion about the main character:
I like that Gwyna was so adaptive to her new situations. She had to learn the life of a soldier than drastically switch to learning how to live a life as a lady's maid. I also like that Gwyna was so loyal. She risked her life to do Myrddin's bidding when he asked her to pretend to be a lake spirit. She also risked her life to warn and help Gwenhwyfar escape when King Arthur found out about her infidelity.