Baek Chan-Mi was once a legendary black agent for the National Intelligence Service. However, after a mission gone wrong that cost the life of her subordinate and allowed her target to escape, she was reassigned to a cybersecurity role. Stripped of her field duties and haunted by the past, Chan-Mi’s chance for redemption arrives when she’s sent undercover as a secretary at Ilkwang Hitech, South Korea’s largest company, to investigate a case of intellectual property theft. Posing as Baek Jang-Mi, she teams up with two unlikely allies—Im Ye-Eun, a glamorous single mother, and Hwang Mi-Soon, an unassuming housewife with a hidden identity. Together, they dive into a world of corporate espionage, secrets, and danger. Meanwhile, Ilkwang’s CEO, Yoon Seok-Ho, can’t shake the feeling that his new secretary, Jang-Mi, who bears a striking resemblance to his former tutor and crush but claims a different name and age, may be hiding far more than she lets on.