It was the worst epidemic in this country's history, and the search for its cause is still one of science's most urgent quests.

It was 1918, the last year of World War 1. Thousands of men lived in the crowded army training camps that were scattered all across the United States. That spring, a strange flu struck the soldiers at a camp in the Midwest. Healthy young men went to the hospital complaining of sore throats and fevers. Within hours they had suffocated, their skin taking on a terrible purplish hue.

The devastating flu spread like wildfire across the country, infecting soldiers and civilians alike. It killed more than half a million people in a matter of months, then disappeared as suddenly as it had come.

To this day, no one knows what caused a common flu to become so deadly, but scientists are still searching for answers. What they discover could save millions of lives if another common flu virus suddenly turns into a killer. In this riveting account, acclaimed nonfiction author David Getz tells young readers the story of the mysterious flu known as the Purple Death -- the virus responsible for the worst epidemic in American history.

David Getz is the award-winning author of the middle-grade novels Thin Air and Almost Famous, and the nonfiction books Life on Mars, Frozen Man and Frozen Girl. When not writing, Mr. Getz works as an elementary-school principal in New York City.

Peter McCarty is the Caldecott Honor-winning author and illustrator of Hondo and Fabian. He also teamed up with David Getz on Frozen Man, Frozen Girl, and Life on Mars. Mr. McCarty lives with his wife and two children in Upstate New York.