“The only time I ever saw something that I thought was abnormal…there was a human arm in the refrigerator,” said J. Peter Willard about his aunt, Mary Louisa Willard. Otherwise, he insisted, she was just “very normal.” But Mary Louisa Willard, a chemistry professor at Pennsylvania State University in the late 1920s, left a strong impression on most people, to say the least. Her hometown of State College, Pennsylvania, knew her for stopping traffic in her pink Cadillac to chat with friends and for throwing birthday bashes for her beloved cocker spaniels. Police around the world knew her for her side hustle: using chemistry to help solve crimes.