Throne of Glass opens with our fierce assassin, Selena, being escorted through the salt mines of End of Year by Kael, the captain of the guard. There, she is brought before Dorian Haveliard, the crown prince of Adderlin. Dorian proposes freedom to Selena in exchange for becoming the King's champion, a title determined by winning the competition sponsored by Nobleman. Dorian finds Selena intriguing, but Kael remains skeptical and hostile, displaying a profound lack of trust during their journey. Kael, as the captain of the guard, places soldiers around Selena's apartment upon their arrival and rifthold, emphasizing his deep mistrust. In her new living quarters, Selena, despite being adorned in fine attire, continues plotting her escape, crafting makeshift weapons from hairpins. Kael restricts her access to the library, but she seeks permission from Dorian and receives a stack of books. Afterward, Kael escorts her to a meeting with the King, where she joins the other competitors. Predictably, all the contenders are male. One participant, Kane, the champion of Duke Parrington, appears particularly fierce and hostile. From that point on, Selena must adopt the alias Lillian Gordena, a jewelry thief from Bell Haven. Kael wakes Selena up early for her first day of training with the other competitors. Kael instructs Selena to not draw attention to herself and to avoid elimination by staying in the middle. Selena, who loves to show off, begrudgingly agrees. Brulo makes them run a long distance, and Selena is so exhausted that she vomits afterward. In the afternoon, they stroll around the castle and unexpectedly encounter Kael, a young woman brought to Adderlin by Duke Parrington, aspiring to become the future queen. She's introducing a new girl, Nahemia Yitgar, an Ilewe princess, who states that she has come to Rifthold to learn their language. Selena converses with Nahemia in Ilewe, a language she picked up from fellow slaves in end of year, and establishes her first friendship with a lady. They leave Coltaine behind and accompany Nahemia to her quarters. Nahemia, who is cherished by her people, is currently facing small rebellions as the King of Adderlin attempts to take control of Ilewe for himself. The day before the first test, Kael misses their session, and a competitor, Bill the I-Eater, is found murdered. The first test comes around, and it turns out to be archery. Selena deliberately downplays her skill to avoid drawing attention, noting that Cain excels as expected. During a morning run with Kael, Selena opens up about her scars and recounts her harsh experiences in the salt mines. Shortly after a test, another competitor is found dead, ripped apart with his insides missing. While strolling in the park with Nahemia, Selena notices a symbol carved into the ground near the clock tower, reminiscent of one she's encountered before. When questioned, Nahemia denies knowledge of their purpose and advises Selena to avoid them, revealing that they're known as weird marks. Selena was not invited to the Samhoo in celebration, during which she stumbles upon a hidden door behind a tapestry, leading to underground passages. That night, Selena dreams of navigating the passage to discover a room adorned with weird marks and the sarcophagi of Queen Elena Haveliard, daughter of Brandon, and the first queen of Adderlin. She encounters Elena's ghost, who reveals that Selena must compete to destroy evil in the castle, understanding the people's plight. Elena gives her a piece of metal, a kiss on the forehead, and a golden necklace, urging her to fulfill this destiny for Erelaya. During the next few days, another murder has taken place in the same gruesome way as the others, clearly becoming a pattern. Selena, intrigued by the word marks, finds strange theories and something called word gates when searching in the library, Kale informs Selena of another murder and invites her to investigate with him. They find weird marks drawn in blood at the crime scene. In the middle of the night, Selena gets another visit from Elena, who reminds her that she needs to win the competition. While heading to her room, Selena encounters Kane, who appears to approach her strangely and struggles to breathe. She observes that he has grown physically stronger during the competition, noticing the gleam of his black ring, and he abruptly rushes away without uttering a word. In the middle of the night, while reading, Selena accidentally drops her book and discovers weird marks drawn in chalk under her bed. Desperate for answers, she heads to the library, where she finds Nihemiah reading an advanced book in perfect common tongue, raising suspicions about Nihemiah's involvement in the word marks and murders. Selena receives a bag of candy from Dorian, and later a gift of the pup she wanted to be saved. Despite concerns about Nihemiah, she decides to dress up for the Yuleema's ball. Selena makes a grand entrance at the ball, dances with Dorian, realizes Nihemiah is not guilty and slips away, but Dorian follows her and kisses her good night. Throughout the book, there is noticeably a lot of chemistry and flirting going on with Selena and Dorian, all the while Kale is jealous and wishes that were him. Returning to the secret passage, Selena discovers Kane drawing word marks and summoning a monster called a Ritterak. After a fierce battle, she ends up in Elena's room, takes the sword, and kills the monster, but is bitten. Barely making it to her room, she passes out from poison. Nihemiah finds and cures her using word marks. In the finals, Kaltane plans to poison Selena. However, when facing Kane, she is poisoned with bloodbane, leading to disorientation and hallucinations. Kale encourages her, and Nihemiah discreetly uses word marks to create a space between worlds, allowing Elena to heal Selena. With a glowing mark on her forehead, Selena overcomes injuries, defeats Kane, and is declared the victor. Nihemiah reveals her family's knowledge of word marks, and she came to Adderland to monitor the king. Kale returns, and they toast to her freedom. Selena signs a contract with the king, who warns her of consequences if she doesn't return from a mission, leading to her agreement.