There is an old profession in this world called "doorlocker". Not a locksmith, but someone who locks doors for dead people. After a person dies, his soul remains. If the door is not locked with three "yin locks", the deceased will walk out of the door during the first seven soul nights - either to visit relatives or to take others away.
There are three types of people who lock the door but do not lock it: those who have died violently, those who have found dead children, and those who have red paint on the door.
The protagonist Chen Sanjin is the last lock-up person of this generation. He guards an old street in the town and runs a shop without a sign. He repairs locks during the day and locks the door at night.
