Sade is Alchemist and Scarlett's youngest child and daughter. She was born with complications that caused intellectual disabilities.
When Sade was around five years old, Alchemist attempted a prefrontal lobotomy to try to cure her intellectual disabilities. Due to complications during the surgery, she was left permanently incapacitated — a decision that weighs heavily on Alchemist's conscience and speaks to the dangerous intersection of science, love, and hubris that defines his character.
The Failed Surgery: Alchemist's attempt to cure Sade's intellectual disabilities through a prefrontal lobotomy ends in permanent incapacitation — one of the most emotionally significant failures in his story arc.