What strange and sinister secret is lurking at the home of Saxby's classmate? Who is the shadowy person in need of Saxby's help, and why won't they reveal their identity? Why is the school's most notorious bully suddenly being nice to everyone? Here are three more mind-baffling mysteries in this absorbing book about Saxby Smart, schoolboy private detective! Saxby reveals the clues that solve the cases but are you 'smart' enough to work out the answers?