The Lost and Found

Harper is the mother of Quicksilver and a mutant. Erik left before Peter was born and she had to live with her sister. She posed a threat to the American government because she was accused of spying since Harper once was part of the CIA. They only accused her when they discovered she was a mutant. Harper were taken from her sister's house but had to be rushed to the hospital because she was in labour. After she gave birth, her sister adopted Peter and they took her to a remote prison (the prison in the X-Men Apocalypse) and experimented and tortured her for years. Harper's jail cell prevented her to use her powers but it did not matter since she never tried to escape.