Fog rolls over gaslit London, and a new detective is on the case: twelve-year-old Wiggins, leader of the Baker Street Irregulars, Sherlock Holmes's secret army of street children. When a stolen naval document, a vanishing racehorse and a two-hundred-year-old family riddle collide into one baffling mystery, Wiggins and his gang of pickpockets-turned-sleuths must follow the clues from foggy Baker Street to a crumbling country manor, and finally to the smugglers' docks of the Thames. Packed with secret codes, hidden treasure, daring chases, loyal friendship and razor-sharp deduction, this thrilling Victorian detective adventure proves that you don't need a magnifying glass or a famous name to crack the case: just courage, cunning, and a gang you can trust.