Gullible yet cheerful Shin Ji-hyun (Nam Gyu-ri) is living a perfect life: she is the only daughter of wealthy, doting parents and is surrounded by supportive best friends. She is also engaged to be married to the perfect man, Kang Min-ho (Bae Soo-bin), in just a few weeks. Meanwhile, Song Yi-kyung (Lee Yo-won) is in an existential crisis following her boyfriend's tragic death. She works third shift at a convenience store, sleeps in the afternoon, and often spends what little time she has left in the day contemplating suicide.
One fateful day interweaves the two characters' stories as Yi-kyung attempts to kill herself by walking into oncoming traffic. A bystander saves Yi-kyung by pulling her out of harm's way. However, a massive pile-up ensues from her actions. Ji-hyun fails to hit the brakes as she approaches the collision site and crashes into a truck. When she regains consciousness after the accident, she shockingly finds that she could neither make physical contact with the people crowding around her car nor could any of them hear her protests. She also sees her own body being carted into an ambulance. A motorcyclist nearby seems to be the only person who can see her. After Ji-hyun leaves him to follow the paramedics attempting to revive her body in the ambulance, she meets the cyclist again at the hospital. The cyclist reveals to her that he is indeed the "Scheduler," an angelic being charged with guiding souls to their final destinations. He explains that since it was not yet her time to die, she is given the chance to recover from her comatose state and live again. The offer is contingent, however, on the completion of a mission: Ji-hyun must gather three teardrops shed out of pure love by three people not related to her by blood within the next 49 days. Elated by the seemingly easy task, Ji-hyun immediately thinks of her fiance and two best friends and is certain she will live again. She then finds herself in the body of the suicidal Yi-kyung for which she will remain for the duration of her quest.
Ji-hyun proceeds by seeking employment as a waitress at a restaurant owned by her high school friend, Han Kang (Jo Hyun-jae). While in the process of obtaining her proof of employment at a hotel where the real Yi-kyung worked, Ji-hyun's memory begins to return to her. Before the accident, Ji-hyun had agreed to meet up with her best friend Shin In-jung (Seo Ji-hye) to show her the bridesmaid dress Ji-hyun had chosen for her. Ji-hyun's excitement is muted when she makes an earth-shattering discovery that opens her eyes to the deception around her. She soon realizes with painful clarity that her life was not so perfect after all and that it won't be as easy to find people who truly love her.
A despondent night-shift worker who lives in a run-down apartment alone. Yi-kyung is shown to be stoic and chronically depressed, with no interest whatsoever in living after her boyfriend's death. She partly contributes to Ji-hyun's fatal traffic accident as she unsuccessfully tries to end her life, one of many attempts. She develops a bond with Ji-hyun and rediscovers the strength to go on living from that friendship and after moving on from her tragic past. She was later revealed to be Ji-hyun's lost sister, Ji-min.
A beautiful, pampered yet kind bride-to-be. From the start of the series, Ji-hyun evinces deep feelings for her seemingly perfect fiance, and strong attachment to her friends. She is nicknamed "Optimistic Princess" by her friends because she was known to view situations through rose-colored glasses prior to the accident. Throughout the drama, Ji-hyun develops the most as a character. While she gradually learns to accept the harsh realities of life, she is still able to maintain her faith in the goodness of others.