This "engrossing study" of invisible ink reveals 2,000 years of scoundrels, heroes and their ingenious methods for concealing messages (Kirkus). In Prisoners, Lovers, and Spies, Kristie Macrakis uncovers the secret history of invisible ink and the ingenious way everything from lemon juice to Gall-nut extract and even certain bodily fluids have been used to conceal and reveal covert communications. From Ancient Rome to the Cold War, spies have been imprisoned or murdered, adultery unmasked, and battles lost because of faulty or intercepted secret messages. Yet, successfully hidden writing has helped save lives, win battles, and ensure privacy—at times changing the course of history. Macrakis combines a storyteller's sense of drama with a historian's respect for evidence in this page-turning history of intrigue and espionage, love and war, magic and secrecy. From Ovid's advice to use milk for illicit love notes, to John Gerard's dramatic escape from the Tower of London aided by orange juice ink messages, to al-Qaeda's hidden instructions in pornographic movies, this book charts the evolution of secret messages and their impact on history. An appendix includes kitchen chemistry recipes for readers to try out at home.