For the past year, 18-year-old Celaena Sardothien has been imprisoned in a slave camp. Chaol Westfall, captain of the Royal Guard, retrieves her. Celaena, trained to be an assassin since she was 10, was one of Adarlan’s most effective assassins before she was caught and sentenced to the slave camps by the king.
Chaol presents Celaena to Dorian Havilliard, Crown Prince of Adarlan, who has a proposal for her. The king is holding a competition to choose a champion, and Dorian wants Celaena to be his candidate. If Celaena wins, she must work for the king for four years as his champion, his assassin; afterward she will have her freedom. While Celaena despises the king, a tyrant who has banished magic, conquered kingdoms throughout the land and enslaved countless people, she accepts the proposal as it offers her a way out of the slave camp and freedom.
A year in the slave camp has left Celaena malnourished, scarred, weak and haggard. Prior to imprisonment, Celaena’s life as an assassin afforded her luxurious clothing and rich food, things that she wants to go back to. She will be competing against other assassins and criminals, so she knows she must regain her strength and skill.
Due to her notoriety and reputation, Chaol and Dorian decide that no one should know Celaena’s identity. She is given spacious rooms and outfitted with beautiful clothing appropriate to the person she is pretending to be: Lady Lillian Gordaina, a noblewoman and jewel thief.
Celaena is one of 24 competitors — made up of criminals, thieves, assassins and murderers —all sponsored by noblemen in the king’s court. Over the course of 13 weeks, she must compete against these men, and while she doesn’t consider most of them a threat to her victory, Cain, a massive and brutal man, is the exception. Duke Perrington, the king’s closest adviser, is Cain’s sponsor.
The competition consists of various contests, with the poorest performers being eliminated and sent back to the prison they were taken from. To regain her skill and strength, Celaena pushes herself through Chaol’s vigorous training regimen. Much to her chagrin, Chaol orders Celaena to have mediocre performances during the competition to save her best efforts for the end. She successfully holds back until she feels compelled to save the life of a fellow competitor during a challenge after he is sabotaged.
As the competition progresses, strange things begin happening in the castle. Competitors are murdered; their bodies ripped open and internal organs removed. Also, symbols known as Wyrd marks are written in blood around each body.
Celaena is alarmed by the killings. They appear to be caused by an animal. Once she has an unsettling dream, she decides to investigate the murders.
One night, Celaena feels a draft in her room and finds a secret passage leading down to crypts beneath the castle. While she finds a possible escape route out of the castle, she doesn’t fully explore the passages but has a dream about them when she returns to her room and falls asleep. In the dream, one passage leads her to the mausoleum of Adarlan’s first king and queen: Gavin and Elena.
In the dream, Elena appears to Celaena and explains that the king’s clock tower in the castle gardens serves as a portal between worlds. Something evil dwells in the castle and must be destroyed before a portal is ripped open and cannot be closed. Elena tells Celaena that she must find and destroy the evil in the castle, and she must win the competition.
Elena gives Celaena an amulet to wear for protection, an amulet that she holds after she wakes up. The next day, Celaena searches the mausoleum to look for clues. She doesn’t find anything.
While living and training in the palace, Celaena makes a new friend, Nehemia, princess of Eyllwe, a nation that has been conquered by Adarlan. Celaena feels a bond with Nehemia. They both feel like outsiders, and both are from nations that have been conquered by Adarlan.
Celaena also makes an enemy out of Kaltain, a beautiful noblewoman who is romantically interested in Dorian. Kaltain sees Celaena as a threat to her plans to marry the prince. Celaena’s relationships with Chaol and Dorian change because both develop romantic feelings for her.
Celaena shows up uninvited to a royal ball. She asks Chaol to dance, but he refuses because Duke Perrington, who knows Celaena’s identity, is watching and would disapprove. She dances with Dorian instead.
Afterward, he meets her in her quarters, and they kiss several times. Despite his father’s warnings against having a romantic relationship with Celaena, Dorian becomes determined to be with her. After Dorian leaves, Celaena walks onto her balcony. Chaol watches her from the gardens below. He sees how happy Celaena is and knows she is thinking about Dorian.
While Celaena spends her daylight hours training or competing, at night she reads books from the ancient castle library, attempting to decipher the Wyrd marks that were left around the murdered bodies. In an ancient book, she finds information that the Wyrd marks are used in a sacrifice. Once a monstrous creature, a ridderak, has been summoned through a Wyrdgate, the symbols guide the beast to the victim. The person summoning the creature offers the victim as a sacrifice in exchange for the victim’s strength.
The only place to summon and hide a creature like the ridderak is the secret tunnels beneath the castle. Celaena ventures down to them and sees Cain, the largest and strongest competitor, chanting as he summons the beast. Cain sees Celaena and locks her in the passageway with the ridderak, changing his plans and using her for the sacrifice since she discovered him. Celaena rushes to the mausoleum to retrieve Gavin’s legendary sword, Damaris, to kill the ridderak, but it bites her before she stabs it to death. The wound almost kills her, but Nehemia finds her and heals her using Wyrd magic.
Celaena recovers and competes so well that she wins her place in the final competition against Cain, who has grown very strong from stealing the strength of the competitors he sacrificed to the ridderak. Despite Cain’s brawn, Duke Perrington has talked Kaltain into spiking Celaena’s drink before a required toast. Celaena unknowingly ingests the poison, which dulls her senses, making it easier for Cain to severely batter her.
As Cain gloats over her poisoned, broken body, Chaol encourages her from outside the ring while Nehemia, using Wyrd magic, summons Queen Elena for help. While some others watching the contest can’t see the queen, Elena appears to Celaena and removes the poison from her body. With the poison gone, Celaena manages to defeat Cain and is declared the winner. After the defeat, Cain tries to stab Celaena in the back, but Chaol sees the impending attack and kills Cain before he can stab Celaena.
Chaol, haunted by killing Cain, visits Celaena as she is recovering. Celaena knows that Cain was Chaol’s first kill, and she understands how he feels. Dorian walks into Celaena’s room as she and Chaol share an embrace, and he can sense that there is now a connection between them.
Chaol leaves abruptly just before Dorian tells Celaena that the contract with the king is ready to be signed. Celaena breaks off the relationship with Dorian, telling him that they cannot be together if she is serving as the king’s assassin. Dorian wants to continue the relationship and suggests that they be together in secret, but Celaena refuses. She asks that they remain friends, and Dorian agrees. When Chaol visits Celaena later that day, she tells him that she ended things with Dorian.
Celaena signs the contract to be the king’s champion, his assassin who carries out his every request without question. The king warns her that if she fails to fulfill the contract or return from an assignment, he will kill Chaol, then Nehemia and her entire family. While she dreads what the king will ask her to do, Celaena can’t help but yearn for the freedom she will receive after four years.