The Valley of Fear : Sherlock Holmes: Book #5

The deadly hand of Professor Moriarty once more reaches out to commit a vile and ingenious crime, but a mole in Moriarty's criminal organization alerts Sherlock Holmes of the evil deed by means of a cipher.

When Holmes and Watson arrive at a Sussex manor house they appear to be too late. The discovery of a body suggests that Moriarty's henchmen have been at work. But there is much more to this tale of murder than meets the eye.