Prosecutor Mu Qing investigated a case that was suspected of being an accidental death and found that it was very similar to the content of Sherlock Holmes novels. In another corner of the city, Chen Wei, the owner of a detective bookstore, is involved in a murder case. The three friends seem to be helping each other, but they each have their own secrets. Under Mu Qing's investigation, seemingly unrelated events eventually point to their obscure past...