The tale unfolds with Geralt's mentor and fellow witcher, Vesemir, rescuing a noble child from a Lechen in the wooded outskirts of Ard Carraigh, the capital of Kaedwen. Just before its demise, the Lechen utters a cryptic message to Vesemir.
The narrative then rewinds several years, showcasing a younger Vesemir, who, alongside his close friend Illyana, begins his journey as a servant to a noble whose mistress has mysteriously succumbed to madness. A witcher named Deglan deduces that the lady is under the influence of a Mahr and, with Vesemir's assistance, successfully exorcises the monster. Before departing, he generously gifts a portion of his fee to the young Vesemir and hints at the possibility of him becoming a witcher.
Prompted by this invitation, Vesemir travels to Kaer Morhen. After enduring years of harsh training and transformative experiments, he emerges as a competent witcher, renowned for his skill with a blade as much as for his brash demeanor.
Fast forward to the present, Vesemir receives a visit from the Elf Filvandrel, who reveals that the Lechen spoke in an ancient, forbidden language, indicating that the forest is ensnared by a powerful curse. Meanwhile, Tetra Gilcrest, a Sorceress from the Kaedwen Court, ventures to persuade the King into wiping out the witchers, branding them as abominations. However, her pleas fall on deaf ears, thanks to the dedicated efforts of Lady Zerbst, who sympathizes with the witchers and their plight.
Upon returning to Kaer Morhen, Vesemir uneasily oversees the training of a youthful Geralt, Coën, Lambert, and Ezekiel. Soon after, Vesemir and another witcher, Luca, find themselves arrested for the murder of two knights who had insulted them during a skirmish. Tetra urges the King to impose capital punishment on the captured witchers, but Lady Zerbst convinces him to send Vesemir along with Tetra to cleanse the forest of its curse instead.
As they navigate through the forest, Vesemir and Tetra encounter a hybrid humanoid named Kitsu, who unleashes a Basilisk upon them. Vesemir bravely vanquishes the beast, but ultimately fails to intercept Kitsu as she retreats deeper into the woods.
Pursuing Kitsu, the duo stumbles upon an abandoned Elven school, where they discover the remains of numerous female elves. They manage to rescue Filvandrel, who departs with a young hybrid girl, vowing that if she ever causes harm, he’ll call upon Vesemir's blade.
In a significant revelation, Vesemir learns that the creatures they encountered were genetically engineered using arcane knowledge only accessible to the Mages of Kaer Morhen. Returning to confront his mentor, Deglan, Vesemir is met with shocking news: Deglan admits to the creation of these monsters owing to a decline in witcher jobs, resulting from a scarcity of real monsters. But before Vesemir can act on this revelation, the fort is besieged by the townsfolk of Ard Carraigh and swarms of monsters from the marshes, all orchestrated by Tetra, who reveals her allegiance with Kitsu.
Lady Zerbst, ultimately unveiled as an aged Illyana, helps usher the young wards of Kaer Morhen to safety while the witchers resolutely defend their home. Despite their courage, they are overwhelmed by the sheer force of monsters and enraged humans. Witnessing the futility of their fight, Deglan attempts to stave off the onslaught as Vesemir confronts Tetra, who has imprisoned the mages within the depths of Kaer Morhen.
Kitsu ensnares Vesemir in an illusion, showing him a life where he had married Illyana and fathered a child. Seeing through this deception, he ultimately kills Kitsu. In a final confrontation, Tetra ambushes Vesemir from behind, unveiling her bitter past where she witnessed a witcher slay her mother, inciting her deep-seated hatred. Just as she seems poised to finish Vesemir off, Deglan intercedes and ends her life, urging Vesemir to guide the children to become "better men" before succumbing to his wounds.
Eventually, Vesemir takes Illyana to a lake—fulfilling a wish she had once shared with him in their youth. They share an ephemeral moment before Illyana passes away peacefully. With a heavy heart, Vesemir reunites with the children, offering them their witcher medallions and empowering them with a choice: to embrace the life of a witcher or walk away.
Geralt voices the common sentiment of disdain towards them, prompting Vesemir to smirk and reply, > "There will always be more monsters, Geralt." The boys ponder Vesemir's words, ultimately deciding to take up their medallions and embark on their own witcher journey.
