Jeong Do-won

An ex-special agent CHA Tae-shik's only connection to the rest of the world is a little girl, So-mi, who lives nearby. Her mother, Hyo-jeong smuggles drugs from a drug trafficking organization and entrusts Tae-shik with the product, without letting him know. The traffickers find out about her smuggling and kidnap both Hyo-jeong and So-mi. The gang promises to release them if Tae-shik makes a delivery for them, however it actually is a larger plot to eliminate a rival drug ring leader. (imdb)

Her daughter died from chain-smoking and she blamed herself too much that her brain coped with the tragedy by erasing her daughter's death from her memories.