故事发生在十九世纪末，闻名世界的大侦探歇洛克·福尔摩斯住在伦敦贝克街221B号。伦敦这座恢宏帝都阴雨连绵，雾气弥漫，警方在抓捕罪犯方面常常束手无策。幸亏有福尔摩斯假以援手，不过案子也得足够有趣才能吸引他参与。

福尔摩斯足智多谋，但聪明人经常对朋友没什么耐心。“动动脑子，华生!”他会这样不客气地跟那位优秀的医生说话。尽管华生医生没他聪明，反应也不如他快，可有时候他也需要华生医生帮忙，而且他对华生的帮助也心怀感激，尤其是在情势危险的时候。

It is the end of the nineteenth century, and Sherlock Holmes, the world-famous detective, lives at 221B Baker Street in London. The great capital is a rainy, foggy city, where the police often have difficulty in catching criminals. Luckily, Holmes is there to help them, but only if a case is interesting enough.

Holmes is extremely intelligent, and intelligent people are often impatient with their friends. 'Think, Watson!' he says sharply to the good doctor, who is not as clever or as quick as he is. But he sometimes needs Dr Watson's help, and is grateful for it, especially in a dangerous situation.