Oh Ha Na, a hard-working career woman, has been best friends with Choi Won, for seventeen years. When Ha Na gets dumped by her boyfriend on her thirty-fourth birthday for a younger woman, Choi Won exacts revenge.

Ha Na has to go back to work and face the consequences for Choi Won's actions. The marketing team gets a handsome new intern.

Ha Na meets Lee So Eun. Meanwhile, rumors about Ha Na and the new intern circulate around the company.

Ha Na wakes up in the same bed as Won, and awkwardness follows when she realizes that she can't stop thinking about it.

Ha Na's ex-boyfriend comes back, and wants to reconnect with her. Won tells So Eun that he is not interested in dating her.

Won does everything he can to keep Cha Seo Hoo away from Ha Na, while Ha Na begins to recall the good moments in her relationship with Seo Hoo.