From the back cover:

The adventures of the Baker Street Irregulars continue in the second volume of the award-winning comics series based on Arthur Conan Doyle's Sherlock Holmes.

The Baker Street Four, Vol. 2 takes our young heroes from the elegant streets of uptown London to the sinister halls of Bedlam. Together, Billy, Charlie, and Tom -- and Watson the cat -- face new missions and new enemies, including the terrifying murderer Bloody Percy.

And nothing can prepare them for the news from Reichenbach Falls: Sherlock Holmes, the renowned detective and mentor of the three friends, has perished. Struggling with shock and grief, the Baker Street Four embark on their darkest adventure yet.