The protagonist inherits a small-town grocery store on the verge of closing. One day, he discovers that opening the store's back door leads not to the stockroom, but to different times and places:
- Monday: The border battlefield of ancient times, during the Western Han dynasty under Li Guang
- Tuesday: Shanghai in 1928, during the Republican era, amid gang warfare
- Wednesday: A wasteland of the future, in 2157, where radiation is everywhere
- A random world appears each day, and everything resets at midnight
