katie was born to a father and mother she would never know, her mother who had been exposed to the mk ultra experiments run by dr martin brenner. the moment of katie's birth, she was removed from the hospital and her parents' arms, and was stolen away to the hawkins lab. for the first years of her life, she was raised in isolation by scientists and dr brenner. though her powers didn't develop until she was older, tests were still ran on her. when she was four years old she was integrated into the same program as the other children of the lab, and became mostly their responsibility. her name was twelve, though she later gave herself the name 'katie' along with the encouragement of the other children of the lab.
kate was raised by fellow experiments, most notably lune, sar, james, emma and one, who were the eldest of the lab by the time katie arrived (by this time, three and seven were already deceased). she grew up under their guidance and was loved—and unlike the other children of the lab, she was able to make memories with them of how it felt to be loved by a family.
she was nine years old when she, sar, lune and james broke out of the lab. the plan had initially been to take all of the children, but complications with the guards prior to that moment meant it was whoever they could grab. it was katie's responsibility to blow open the outer wall with her energy blast, though it sapped most of her energy almost immediately. she was able to keep deflecting the bullets with said powers as they ran. as lune made her sacrifice, katie ran on ahead with james, and was the first to squeeze through the tunnel and gates to freedom.
she lived with james in wyoming for three years, after sar left them to venture on her own. there, she slipped easily into school and a semi-normal life. james cared and provided for her, while the both of them remained a steady telepathic connection with sar, who was in chicago. after receiving increasingly worrying messages from sar—who had returned to their hometown of hawkins—regarding monsters and hawkins lab, both katie and james crossed the country to once again reunite with her. katie ultimately saved sar and her friends from the demogorgon by using her powers, and became integrated into sar's new life and sar's biological father, jim hopper.
