In the summer of 1894, John Addington and Henry Ellis begin writing a book arguing that what they call “inversion,” or homosexuality, is a natural, harmless variation of human sexuality. Though they have never met, John and Henry both live in London with their wives, Catherine and Edith, and in each marriage there is a third party: John has a lover, a working class man named Frank, and Edith spends almost as much time with her friend, Angelica, as she does with Henry. Shortly before the book is to be published, Oscar Wilde is arrested. John and Henry must decide whether to go on, risking social ostracism and imprisonment, or to give up the project for their own safety and the safety of the people they love.