Tells the story of unpredictable events that take place in the close relationship between a perfectionist Wan Jun, his girlfriend Ji Yeon, and Ye Ri, who has a crush on Wan Jun .

Young-mi, the bookkeeper at a factory, is ridiculed for her dowdy appearance and called ‘Ms. Apocalypse’ by her colleagues. Do-young, a delivery driver, is the only one to show her any decency and kindness. As her feelings for him grow, Young-mi strives to get him off the hook even when she finds out that Do-young has been embezzling company money. It becomes the last day of 1999, and in the midst of people's fear that the world will come to an end, Young-mi gets arrested for aiding Do-young's crime. And thus, her new millennium starts wretchedly. As she walks out of prison after a few months, she comes across Do-young’s wife, Yu-jin, waiting for her and this unexpected visitor makes an implausible but compelling offer.

In a world where an AI programme allows people to communicate with their deceased loved ones, a flight attendant and a mother question the meaning of reality and humanity.