Sherlock Holmes, the world's greatest detective, hasn't yet made a name for himself. He's 14 and on break from his school. His father's off to India, so Sherlock has to stay with his uncle and aunt--two family members he's never even met. He spends most of his days outside and away from the housekeeper.
Sherlock then meets Matty, a boy living on his own who wanders the countryside. Matty tells Sherlock of a dead person from earlier...and the strange black cloud he saw float out the window after his death. Sherlock thinks he's explained it...until he sees it after stumbling upon a dead body near his uncle's home. A Mr. Crowe comes for the summer to tutor Sherlock and the three of them begin an adventure to solve two murders and unveil a plot to destroy the British Army.
There are definitely slow moments throughout the book, giving you a feel for the scenery as well as the mystery. Sherlock is well-drawn, as are his compadres. When the action starts around halfway through the book, the pace picks up a bit and it goes faster.