Inside the Louvre in Paris, it was a sweltering summer day and an overweight guard had eaten too much cassoulet at lunch. He was lethargic, drooping. When he left that evening, Leonardo da Vinci's masterpiece The Mona Lisa was hanging on the wall. When the museum opened back up two days later, all that remained "were four iron hooks and a rectangular shape several shades deeper than the surrounding area." The world's most famous painting had been stolen.