Making a mistake after having way too many drinks can change everything. Lee Gun (Jang Hyuk) is the successor to a large company run by his family. Kim Mi Young (Jang Nara) is an average-looking secretary in a law firm who earned the nickname “Post-It” for her inability to say no to her colleagues who dump work on her. When the two cross paths one night after having too much to drink, they end up having a one-night stand. When Mi Young finds out afterwards that she is pregnant, what will become of them? And will Nam Se Ra (Wang Ji-won) and Daniel (Choi Jin Hyuk) just stand by and let Gun and Mi Young deal with the situation in their own way?