When misadventure led a schoolboy in London to employment at Baker Street, few could have guessed where his introduction to Sherlock Holmes would lead. But as the lad matures and he finds himself caught in the middle of a murder investigation, his friendship with Holmes and Watson lures him into the role of detective. 'Billy' documents his experiences, and soon his sleuthing skills not only bring him to another murder, but also lay the foundation for his metamorphosis into a famous mystery writer.

London in 1890 is shocked by a series of gruesome murders. There seems to be no rhyme or reason to them, except for their location in the Thames dockland. Scotland Yard is perplexed. Can Sherlock Holmes and Dr. Watson help before worse follows? And what is really going on?

At Oxford they jokingly called themselves The Seven Sinners. Now, 30 years later, they are being murdered - each in the manner of his particular 'sin'. Who is doing it and what is the connection with the twin serpents, the mysterious Emerald Lady and the holy Book of Kor? Holmes and Watson -with the aid of their new friend, Professor Challenger - must race against time and the killer...before one of the victims becomes his brother, Mycroft.

Holmes and Watson are handed the challenge of solving the London Tarot Murders, a dark episode which, to quote Dr. Watson's in his memoirs, "occupies a lofty place in the annals of all black deeds ever committed in the long memory of the ancient, regal city, higher even than the infamous affair with the Ripper."

In real life, 221B Baker Street is the home of a bank. When fans send letters to Sherlock Holmes, bank employee Addy Zhuang, known as "Sherlock's Secretary," replies. One day, the bank is robbed, but the thieves only take three letters addressed to Sherlock Holmes. The police conclude it was all a harmless prank, but Addy suspects something more malicious is happening.