Trace identification expert Qi Ming runs a special lost property agency, relying on scientific means such as microscopic analysis to find lost items of profound significance. From gold rings that spark employer misunderstandings to yellowed old photographs bearing elders' memories, he and his assistant Lin Xiao always manage to peel back the layers within subtle traces. However, the severe damage to the items and the clients' deeply hidden emotional knots bring heavy resistance to every lost property retrieval process. Faced with fragmented clues and hidden pasts, how Qi Ming will use professional technology to piece together the complete truth becomes the key to unlocking the regrets deep in people's hearts.