Early 19th century. After the victory over Napoleon, peace reigns in Europe, and Russia is reducing its army and rapidly developing industry and agriculture. Construction is noisy everywhere, and the cities are connected by a network of highways and railways. Intelligence is overloaded with the production of information necessary for the implementation of the industrial revolution. Against this background, strange things begin to happen in the capital of the empire: the most popular coins, the penny, begin to disappear. The situation is threatening, because even the constant issue of money by the mint cannot improve the situation! Detective of the Third Department of the Secret Chancery, Grigory Konovitsyn, takes over the investigation. The book is written based on real events.