Ruin and Rising opens with Alina Starkov, the heroine and narrator, living in an underground city connected to her homeland of Ravka by tunnels. Alina is a powerful Grisha (magician) who has the ability to call and wield light from the sun and stars as a weapon. Her nemesis, the Darkling, who can conjure and control darkness, is her polar opposite. The Darkling has usurped the throne of Ravka, usurping the former king and queen with the help of shadow warriors he has made. Alina wants to fight the Darkling, but she’s weakened underground by her lack of sunlight and the repercussions of a battle with the Darkling at the end of the previous book in the series, Siege and Storm. The Apparat, a religious leader who previously served Ravka’s monarch and now seeks to enthrone Alina, has control of the underground city. Alina fears he’ll try to use her like a puppet, and she’s wary of him. Despite her incapacity to use her abilities, Alina and the Darkling have a psychic link that any of them can act as a result of their powers combining during their last combat.
Alina regains her summoning skills and intimidates the Apparat into letting her and her friends depart with the help of the loyal Grisha who followed her beneath and Mal, her childhood best friend. The party makes its way to the surface, dodging tunnel collapses. Alina, Mal, and the Grisha try to locate Nikolai Lantsov, one of their allies, as they emerge from the tunnels.
Nikolai is the Ravkan King and Queen’s sole surviving son, and he intends to recapture the throne for his family. However, because Nikolai has gone into hiding after narrowly avoiding an attack by the Darkling and ferrying his parents and Alina’s mentor, Baghra (the Darkling’s mother), to safety, Alina can only follow a hunch about where to find him. After failing to locate Nikolai, Ravka’s army deserters attack the group and hand Alina up to the Darkling. Nikolai saves Alina and her friends from the attack and transports them in one of his flying airships to a hidden mountain castle.
Alina reconnects with Baghra at the fortress, who assists her in further developing her summoning power. Baghra also claims that her father was Morozova, a strong sorcerer who invented the Grisha amplifiers and experimented with creation and resurrection. Baghra has the ability to call darkness, but her sister, whom their father resurrected after an accident, did not.
Nikolai then exiles his father for a crime and prepares to contest the throne of Ravka with the Darkling. He makes it clear to Alina that he wants to marry her after the war, despite the fact that the two have no love feelings for each other. Alina, who has been in love with Mal for a long time, is unsure about her decision. Mal admits to having affections for Alina in the stronghold, but he believes he is unworthy of her. Alina reluctantly agrees to contemplate marrying Nikolai, cognizant of the political role she must play as a strong Grisha. She keeps using their psychic connection to contact the Darkling, hoping to break his confidence.
Alina and her friends are getting ready to leave the fortress. Nikolai and Alina intend to travel to West Ravka, Ravka’s western neighbor, in order to gain support for his claim to the throne. Nikolai will then lead her back to the others in pursuit of a third magical object that can enhance Alina’s summoning talents (she has already claimed artifacts from the other two amplifiers in the previous books). A firebird is said to be the third amplifier. However, the Darkling attacks Nikolai and converts him into one of his shadow monsters before any of the friends can leave the citadel.
Baghra, enraged at her son, uses her own darkness-calling abilities to leap from a cliff and capture the shadow monsters, giving the others time to flee. Alina, Mal, and the Grisha escape from the fortress in an airship. By twisting the light that would typically reflect off the airship, Alina makes it invisible to passersby. Nikolai, in his altered form, is following them, persuading her that there is enough of his humanity remaining in him for her to save him.
The company breaks into two after landing at the hilly border of Ravka with its southern neighbor, Shu Han. Alina, Mal, and a group of Grisha set out into the woods in search of the firebird. After days of hunting, they come across the bird, but Alina and Mal discover it isn’t the third amplifier after all. Instead, when Morozova restored Baghra’s sister, he gave her the power he would have given the firebird, implying that she and her descendants are amplifiers.
Mal is the third amplifier and a descendant of Baghra’s sister. Alina is sad since, in order to harness its power, she has always had to kill the animal that served as an amplifier. Mal insists on killing him when the moment is right in order to vanquish the Darkling, and Alina reluctantly agrees if there is no other option.
The party prepares for a final confrontation with the Darkling, who has burned the orphanage where Alina and Mal grew up and converted it into a school for Grisha children. The Darkling kidnaps the children in order to entice Alina to meet him. In the Shadow Fold, Alina, Mal, and the Grisha face off against the Darkling, who created an area of everlasting darkness and demons many years ago. Alina and her warriors utilize the same invisibility cloaking technology they did on the ship, but the Darkling notices them. Alina nearly avoids him and joins Mal nearby in the darkness.
He makes her kill him in order for his power to be released as an amplifier. Alina becomes more powerful for a brief while after being heartbroken, but she loses her summoning skills forever. Instead, Ravka’s army’s non-magical soldiers all have the ability to summon light. Alina kills the Darkling with a Grisha knife, killing him, his army, and the Fold. Nikolai transforms back into a human being. Alina’s Grisha resurrects Mal in the aftermath of the war. She rejects Nikolai’s marriage proposals once more and goes to her homeland with Mal, where they rebuild the orphanage and school and provide care and value to the pupils.