Plot

Escaping from poverty to become a witcher, Vesemir slays monsters for coin and glory, but when a new menace rises, he must face the demons of his past.

The world of The Witcher expands in this anime origin story: Before Geralt, there was his mentor Vesemir a swashbuckling young witcher who escaped a life of poverty to slay monsters for coin. But when a strange new monster begins terrorizing a politically-fraught kingdom, Vesemir finds himself on a frightening adventure that forces him to confront the demons of his past.

The story begins with Geralt's mentor and fellow witcher Vesemir saving a noble child from a Lechen in the forests in the outskirts of Ard Carraigh, the Capital of Kaedwen. Before dying, the Lechen says something to Vesemir.

The story then shifts back several years to a younger Vesemir who along with his best friend Illyana worked as hands for a noble who's mistress had suddenly befallen madness. A Witcher Deglan, deduced that the woman was possessed by a Mahr and successfully exorcised the monster with Vesemir's help. Before leaving, he gave a share of his payment to the young Vesemir and faintly invited to the boy to become a Witcher.

Vesemir taking up the offer went to Kaer Morhen and after years of brutal training and body altering experiments became a successful Witcher, notorious for his blade as well as cockiness.

In the present, Vesemir is visited by the Elf Filvandrel who tells him that the Lechen spoke an ancient and forbidden tongue few dared to speak which proved that the forest is cursed under a powerful spell.

Meanwhile, the Sorceress Tetra Gilcrest of the Kaedwen Court tries to instigate the King to wipe out the Witchers of Kaer Morhen whom she deems to be an abomination. But her words are not heeded due to the zealous efforts of Lady Zerbst who is sympathetic to the Witchers and their cause.

Vesemir visits Kaer Morhen where he reluctantly oversees the training of a young Geralt, Coën, Lambert and Ezekiel.

Later he and another fellow Witcher Luca are arrested for killing two Knights who had insulted them in a fight.

Tetra implores the King to execute the imprisoned Witchers but Lady Zerbst persuades the King to instead send Vesemir along with Tera to the forest to rid the place off the spell.

Venturing into the forest, Vesemir and Tetra meet a female hybrid humanoid named Kitsu who sends a Basilisk after the two. Vesemir successfully slays the monster but is too late to catch Kitsu who flees further into the forest.

Following Kitsu, the pair come across an old and abandoned Elven school where they find the bodies of numerous female elves. They rescue the captured Filvandrel who then leaves the premise with a hybrid albeit young girl swearing that if she ever harms anyone, he'll call for Vesemir's sword.

Vesemir finds out that the monsters he encountered are genetically bred with magic only known to the Mages of Kaer Morhen before leaving for the fort to confront his Mentor and Master Witcher Deglan.

Deglan admits to creating the monsters as according to him, the Witcher's work wad slowly diminishing due to a lack of monsters. But before Vesemir can act on it, Kaer Morhen is laid siege by the townsfolk of Ard Carraigh and numerous monsters from the Marsh led by Tetra who reveals herself to be working with Kitsu all along.

Lady Zerbst now revealed to be an old Illyana escorts the young children at Kaer Morhen to safety while the Witchers defend their home.

Although they put up a good fight, the Witchers are massacred due to the sheer number of the monsters and humans. Deglan, seeing the folley in his actions tries to hold off the horde while Vesemir confronts Tetra who has captured and held the Mages hostage in the basement of Kaer Morhen.

Kitsu arrives and plunges Vesemir into an illusion where he married Illyana and had a child. Vesemir sees through the illusion and kills Kitsu.

Tetra attacks Vesemir from behind, revealing that when she was younger she saw a Witcher murder her mother in cold blood, explaining her hatred for Witchers. Before she can deal the final blow, Tetra is killed by Deglan who asks Vesemir to find the children And make them into "better men" before succumbing to his wounds.

Vesemir takes Illyana to a lake, a wish she had confided to Vesemir when they were young. The two share a brief moment together before Illyana passes away peacefully.

Vesemir then sets out and catches up to the children. He throws them their Witcher medallions and asks them to choose to become Witchers or walk away.

Geralt states that everyone hates them at which Vesemir smirks and replies,"there will always be more monsters Geralt."

The boys contemplate Vesemir's words before picking up their medallions.