A Pledge to God questions people’s views about moral and ethical dilemmas by showing a woman's unfortunate life. Ji Young, a successful female anchor, is having a wonderful life she's dreamed of with her husband, Jae Wook. However, her happiness doesn't last long. She finds out that Jae Wook is cheating on her while she's carrying Jae Wook's child. Jae Wook's affair makes her decide to get a divorce. After going through a hard time, Ji Young marries Min Ho, and they have a son, Hyeon Woo. However, Hyeon Woo becomes terminally ill, and Ji Young is left with a hard choice. She has to either watch Hyeon Woo die or meet her ex-husband, Jae Wook, and accept his deal. What choice will she make? Will she choose to follow her maternal instincts to save her own son and ignore moral and ethical standards?