一天，609号房东花花公子Mum，看到一个小伙在他的床上，从他们第一次见面就上床那天后，神秘的事情不断发生。Mum总是梦见一个神秘的事件，半夜总会被奇怪的梦突然惊醒。Mum试图通过和女人上床来忘记和年轻男子的“情感”。然而，这甚至让他多想想他的梦中情人。然后，他把事件的点点滴滴联系起来，提出了反向平行宇宙的理论。最后，他在现实生活中遇到了Dew。虽然他们的第一次见面是Dew的最后一天，但也是他们两个互相帮助改变未来的开始！
　　One day, a strange man is sleeping on Mum's bed, a playboy and the owner of room 609. They both have passionate sex the first time they meet and after that, mysterious things keep happing. Mum always dreams of a mysterious event and wake up frightened in the middle of the night.
　　Mum tries to forget the "feeling" with the young man by having sex with women. However, it even makes him think of the man of his dream more. Then, he connects the dots of the events and comes up with the theory of reverse parallel universe.
　　Finally, he meets Dew in real life. Though their first meeting is Dew's last day, but also the beginning that both of them will help each other to change the future!