The old library of Qingshi Town is about to close for repairs. Librarian Lin Zhixia receives an anonymous letter, involving an old case from twelve years ago where the Tingyu Bell, one of the Seven Treasures of Qingshi, mysteriously went missing. Together with her friend Shen He and antique restorer Zhou Yanyan, she follows the guidance of letter after letter, visiting Chen Bo the clockmaker and collector Xu Wenshan, and cracking clues hidden in old objects such as an anonymous ancient book, an ancient bronze mirror, and a folding fan. After peeling back the layers, everyone discovers that the so-called theft was actually a misunderstanding caused by data tampering and communication errors. In the end, everyone clarifies the truth, repairs their trust, and allows the Seven Treasures of Qingshi and the town's dust-laden memories to reappear in the reopened library.