Known for her insight and sharp mind, Catherine II was keenly interested in philosophy, medicine and the natural sciences, corresponded for many years with Diderot and Voltaire and invited many outstanding scientists of her time to the court. Among them was an experienced English doctor Thomas Dimsdale, who in 1768 came from London to instill the Grand Duke Pavel Petrovich and (the first of the European monarchs) Catherine herself from smallpox in an atmosphere of the strictest secrecy. In the XVIII century. the "spotted monster," the deadly smallpox virus, devastated Europe, and the empress understood well the threat that the epidemic posed to Russia. The first mass vaccination campaign in Russia, successfully carried out by Dimsdale, laid the foundation for modern vaccination practices. How the secret plan of the English doctor and the Russian empress arose and was implemented is fascinatingly and reliably described in this book.