An email from an unknown source, an ancient house that does not exist on the map, and a secret that has been hidden by the "Construction Society" for three thousand years.
Su Yumu, a graduate student in ancient architecture, received a strange invitation letter to an academic seminar. The sender was a non-existent organization - the "China Ancient Buildings Conservation Association." When he searched according to the address, he found that there was no house number "No. 81" In the capital.
