A five-year-old child is left on the doorstep of Eloise Lancaster, who keeps the child, pretending to be her aunt. Due to her small stature as a child, Eloise sends her to martial arts school. After she graduates a the top of her class, she is recruited by MI5. After a set of strange circumstances, she ends up at MI6. Later, she leaves MI6 to collect her mysterious inheritance in the U.S. from her father, who also worked for MI6 and on occasion, for the CIA. She becomes a detective. After she loses her adult child to Leukemia, she becomes an equalizer.