More than two hundred years have passed since the publication of the literary masterpiece “The Tale of Igor’s Campaign,” but the authorship of the great work has not been established. The reader is drawn into an exciting, almost detective story from the first pages of the book. The first mention of “The Lay” dates back to 1797. The manuscript of “The Lay” was preserved only in an Old Russian collection acquired in the early 90s. XVIII century, one of the collectors, Count Alexei Musin-Pushkin, from the former archimandrite of the Spaso-Preobrazhensky Monastery in Yaroslavl, which was abolished by that time, Joel. The only medieval text of “The Lay” known to science burned in 1812, which gave reason to doubt the authenticity of the work. The author of the book, A. Kostin, proves that “The Tale of Igor’s Campaign” is the greatest forgery in the history of Russian literature. It turns out that the “Lay” was written not in the 12th century, but 500 years later.