Eighteen-year-old Celaena Sardothien survived a year as a slave in the brutal prison camp at Endovier and battled criminals and evil monsters to win the title of King’s Champion. Now she must work as the royal assassin to Adarlan’s evil king for four years to win her freedom. It’s been two months since the competition, and Celaena has been busy fulfilling her new role as the king’s assassin. What the king doesn’t know is that instead of killing his enemies, Celaena has been faking their deaths and helping these men and women sneak out of Adarlan.
When Celaena returns from her latest assignment, she is assigned her next target — a suspected rebel leader named Archer Finn — and given a month to complete the task. Celaena has known Archer for years, since they are both a part of Adarlan’s criminal underground. Celaena doubts that Archer, a popular male courtesan who services the wealthiest men and women in the city, could be involved in a plot to overthrow the king. She aims to find out what Archer knows before figuring out a way to fake his death and get him out of the city.
Celaena has been asked by both the spirit of the Fae queen Elena and Nehemia, princess of the captured kingdom of Eyllwe and Celaena’s best friend, to help find a way to defeat the king, but she has refused. Celaena fears the king’s power and wants to complete her four years working for him so she can finally be free.
While Celaena ended the romantic relationship between her and Prince Dorian after she was named the King’s Champion, her relationship with Chaol, captain of the royal guard, is intensifying. Celaena surprises Chaol with a romantic dinner for his birthday, and they spend the night together but decide to keep their relationship secret so as not to upset Dorian, who is also Chaol’s best friend.
Despite their secrecy, Dorian knows Chaol and Celaena are in a romantic relationship. Though he is jealous, the prince has larger concerns. He is realizing that he has magical powers, the very likes of which his father has outlawed. If Dorian’s abilities are discovered, he will be put to death.
Celaena finds out that the rebel movement’s purpose is to find Aelin Galathynius, the lost heir of the kingdom of Terrasen, hoping that she will take her place as queen and lead a rebellion to overthrow Adarlan’s king. Terrasen was one of the most powerful nations in the land before Adarlan sent assassins to kill the royal family, who were directly descended from the Fae. While the entire country fell to Adarlan’s invading forces, Aelin is rumored to have survived the attack and would now be 18 years old.
The king tells Chaol that there have been death threats made against Nehemia. The king suspects that Nehemia is involved in the rebel movement and intends to question her, but forbids Chaol to tell anyone of the threat or of his suspicions. Chaol agrees but is kidnapped soon after, with a note of his whereabouts sent to Celaena.
Celaena rescues Chaol and discovers that Archer is indeed a part of the rebel group and is also behind the kidnapping. Archer tells Celaena that he and Nehemia are working together to assemble a rebel force to challenge the king. While Nehemia trusts Celaena, Archer does not, especially due to her relationship with Chaol. Archer tells Celaena that Chaol is aware of a plot to assassinate Nehemia and that the king intends to torture and question the princess about her involvement with the group. Archer kidnapped Chaol to stop the interrogation and to prove to Celaena that Chaol is untrustworthy.
With Chaol freed, Celaena rushes back to the castle only to find Nehemia and her guards brutally murdered, their bodies grotesquely displayed. Celaena blames Chaol for the deaths since he knew there was a threat on Nehemia’s life and didn’t tell either Celaena or the princess herself, who could have taken precautions. Celaena tries to kill Chaol, but Dorian saves him using his latent magical abilities to freeze Celaena’s attack long enough for soldiers to help neutralize her.
Celaena, now in a state of overpowering grief, is thrown into a dungeon to regain control of herself. After a few days, she is returned to her quarters where she stays in a deep depression until she decides to hunt down Nehemia’s assassin. She recognizes the way the bodies were brutalized as the work of Graves, a man she competed against and beat in the contest to be King’s Champion. She finds Graves and tortures him to death.
Celaena goes to Nehemia’s quarters to pack up the princess’s things and finds notes containing Wyrdmarks and clues leading to a riddle. Unable to solve it herself, she seeks out an ancient witch working at a traveling carnival. The witch tells her that the riddle describes three Wyrdkeys needed to open the Wyrdgate, a portal to numerous other worlds. A person who holds one Wyrdkey would wield an enormous amount of power, but the person who controls all three would be powerful enough to control the entire world and others as well.
Celaena knows that asking questions like these can get her killed, and she doesn’t trust the witch. The witch suspects Celaena will attack, and so she tries to kill her first. They fight, with Celaena getting the upper hand and killing the witch and burning her body.
Celaena finally deciphers the riddle and goes to find the first Wyrdkey but it’s already gone, the king having found it years before. Celaena suspects that the king has the second key and knows she must find the final key before he does. She thinks Nehemia may know where the keys are, and using a book on magic and Wyrdmarks, she draws symbols to open a portal to another world to reach her friend.
Celaena is successful in reaching Nehemia, who tells Celaena that she knew her fate and allowed it to happen to set events in motion, events that will ultimately lead to the king’s defeat. She also tells Celaena that opening the portal is dangerous and she must never do it again as other things may come out of it. As Nehemia disappears, Celaena sees Archer, who has been hiding and watching her.
Celaena confronts Archer, who admits that Nehemia left the rebel group a week before her death because she didn’t agree with his tactics to bring down the king. Fearing Nehemia would report the group to the king and wanting to drive a wedge between Celaena and Chaol, Archer issued the anonymous death threat and hired Graves to kill the princess.
Celaena attacks Archer. During their fight, she puts a bloody hand on one of the symbols, which changes the portal and summons a horrible creature from another world. Dorian, who was alerted to Celaena’s activities by a dream, arrives with Chaol to see Archer running away and Celaena and her dog, Fleetfoot, fighting the creature. The creature drags Fleetfoot through the portal, and Chaol and Celaena go through to rescue her.
Once in the other world, Celaena changes into her true Fae form. Using her powers of fire, she holds the creatures back long enough for Chaol, Fleetfoot and herself to get back through. Chaol is shocked, and Dorian, having passed out from a blow to the head, missed seeing the secret Celaena has been hiding. She tracks down and kills Archer.
Chaol knows that Celaena will be killed if anyone finds out she is Fae, so he asks the king to send her to assassinate the royal family of Wendlyn, a nation they have been at war with for two years. Wendlyn is the last stronghold of the Fae, and Chaol hopes she will be safe there, abandoning her duties to the king and never return. Celaena knows Chaol means well, but she is anxious to find the Wyrdkeys and doesn’t want to leave Adarlan. Queen Elena appears to her and convinces her to go to Wendlyn.
Before she leaves on the ship, she gives Chaol a clue to who she really is and tells him that she is sorry. Chaol returns to the castle and realizes that Celaena is Aelin Galathynius, heir to the throne and rightful queen of Terrasen. Aelin is the greatest living threat to Adarlan, and she is now on her way to her strongest potential allies in the home of the Fae.