On a hot September day in 1924, Jesus Lajun noticed a terrible smell coming from his house in Los Angeles. He went down to his basement and discovered a dead rat, which he picked up and tossed in the trash. A few days later, Lajun came down with a fever and noticed a strange, purple lump on his thigh. Soon Lajun was dead, as was his daughter, several of his neighbors, his ambulance driver, and even the priest who had performed his funeral. All of...