One of the preeminent natural philosophers of the Enlightenment, Benjamin Thompson started out as a farm boy with a practical turn of mind. His inventions and scientific explorations include the Rumford fireplace, insulated clothing, the thermos, convection ovens, double boilers, double-paned glass and an improved sloop. Successful in world affairs, he was knighted by King George III and became a Count of the Holy Roman Emperor.

Thompson was popular with women - so much so that his personal life eclipsed his achievements. While British spy in the colonies, he had an affair with the wife of Boston printer Isaiah Thompson. In London, he had a fling with the wife of a doctor who would be in the first man to balloon across the English Channel. He fathered a child by the court mistress of the Prince Elector and had affairs with several other German noblewomen. He wrote that his first marriage, to a New England minister's daughter, made his career, and called his second wife, the widow of the French chemist Lavoisier, a female dragon. Drawing on Thompson's correspondence and diaries, this book examines his friendships and romantic relationships.