Gregor and the Code of Claw
Only a few hours have passed since the closing of Gregor and the Marks of Secret, when Gregor returns from the Firelands to warn Regalia of an impending gnawer attack. As the novel opens, Gregor is numb with shock from the Prophecy of Time's apparent prediction of his death. He and his bond Ares disobey Solovet and return to the Firelands to find the terribly ill Luxa, Aurora, and Howard. Gregor rushes his ill friends back to the city for treatment, whereupon Solovet orders him locked in the dungeon for insubordination. He is eventually released by Nerissa to help his sister Boots while the toddler works to fulfill the Prophecy of Time by deciphering the rats' "Code of Claw".
Solovet still wants Gregor imprisoned, until Ripred and Mareth inform her that Gregor has recently developed romantic feelings for Queen Luxa, and would never leave Regalia while she is hospitalized. Shortly after this incident, an upset Gregor is called to the code room for an "emergency with [his] sister", and discovers eight-year-old Lizzie has come to bring him home. When the code team learns that Lizzie has an aptitude for puzzles, Ripred makes the suggestion that she replace Boots. Gregor is desperate to keep his family safe, so he extracts a promise from Ripred to protect them and keep them in the dark about Gregor's impending doom. While Lizzie works on (and ultimately solves) the code, Gregor fights the Bane's armies, struggling all the while to cope with his emotions about Luxa and Sandwich's prophecy.
Shortly before his final confrontation with the Bane, Gregor has all but lost hope for his life. Noticing this, Ripred tells him that he doesn't believe Gregor has to die, because the old rat has never believed in Sandwich's prophetic ability. This revelation inspires Gregor to ultimately defeat the unstable Bane. Two weeks later, a wounded Gregor awakens in the hospital and learns of a series of crushing events. Though the humans routed the rats, Ares died in the Firelands of wounds inflicted by the Bane; Ripred is presumed dead; and Vikus has been partially paralyzed by a stroke brought on by his wife's death.
Though Gregor no longer feels bound by it, many Underlanders wonder how the prophecy can be fulfilled while "the warrior" lives. At the rats' official meeting to discuss terms of surrender, they have their answer. Angered by both a half-dead Ripred and Luxa's readiness to return to war, Gregor breaks Bartholomew of Sandwich's sword on his knees and pronounces the warrior officially dead. Ripred and Luxa, agreeing with Gregor's sentiment, do something unprecedented and bond as a sign of their mutual desire for peace. Afterward, delegates from each species meet to negotiate more a specific treaty while Gregor's family says their good-byes and returns to New York. The novel ends as Gregor's parents discuss a move to Virginia while their children wonder how they can ever forget the Underland. Gregor takes his sisters to the park, where he remains haunted by traumatic memories of the Underland, then notes that Boots has finally learned how to say his name.