Dr. John Snow is one of the most influential doctors and researchers in Western medicine, but before he rose to fame, he was just a simple community doctor who wanted to solve a mystery.

In 19th century London, the spread of cholera was as unstoppable as it was deadly. Dr. Snow was determined to stop it, but he had a problem: His best theory of how the disease was spread flew in the face of popular opinion. He needed evidence, and he needed to find it fast, before more lives were lost.

Taking on the role of detective as well as doctor, Dr. Snow knocked on doors, asked questions and mapped out the data he'd collected. What he discovered would come to define the way we think about public health to this day.

This compelling nonfiction picture book is a timely reminder of the power of science to save lives.