December Fever is a story of a married woman who falls for a younger man, only to discover he is dying of cancer. Oh Young-shin is the model homemaker to her career-oriented doctor husband and her children but eventually wants to become a "bad girl" which leads her to having this secret love affair that is eventually revealed. She is now an unfaithful woman who gave up everything to to pursue this affair only to find out that this younger man is only with her because of a bet he made with his friend and therefore, doesn’t truly love her. In this entangled love story, will the characters end up pursuing happiness?