In The Witcher season 1, episode 8, Geralt is abandoned by his mother, but it's never explained why exactly she does this. Not much is known about Geralt's pre-Witcher origin story, but it is known that his mother's name is Visenna and she is believed to be a druid and healer. She is seen floating an apple over to Geralt in the same scene where she ultimately abandons him. Geralt also sees his mother in adulthood for the first time during a fever dream and she helps heal him. He tries to press her on why she left him and if she knew of the dangers of the mutations that would turn him into a Witcher, but she gives no clear answers.
The Witcher season 2 doesn't offer up any explanation either, so watchers are still left wondering and theorizing why. It's worth mentioning that Visenna appears in a short story titled «The Road with No Return» and was later confirmed by author Andrzej Sapkowski to be Geralt's mother, but this still offers no insight as to why she left Geralt with the Witcher Vesemir. So, that leaves three interesting theories worth examining to get to the bottom of why she would give him to the Witcher order in the first place.
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The first option as to why Visenna may have left Geralt is that Geralt himself was a child of surprise. There is some credence to the theory that Geralt was a child of surprise and thus belonged to Vesemir as his Unexpected Child. In the scene where Vesemir picks up Geralt as a child, it appears as though he is expecting the young boy. It's possible he once saved Visenna and chose the law of surprise as his payment. Vesemir invoking The Witcher's law of surprise with Visenna, resulting in his right to raise
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