As the world battles COVID-19, a team of experts from across the globe are in a race to shed light on how this virus emerged. At the center of their research: bats, often considered patient zero for most of the deadly viruses recently affecting humans. Follow these scientists from the forests of Cambodia to the urban underpasses of Singapore to the bat archives of the Smithsonian's Museum of Natural History and see how these bizarre mammals--and their unique relationship with viruses--may be the key to saving humanity from future pandemics.