When Dr. Catalina Lopez of the Center for Disease Control first receives a report of a lethal new "superbug" immune to all known antibiotics, she realizes that she has a major health crisis on her hands. An ultra-resistant form of group A strep is spreading like wildfire throughout hospitals and emergency rooms in Seattle and the Pacific Northwest. Doctors, lacking any effective way to combat the infection, can do nothing but stand by and watch their patients die, one after another. Dr. Graham Kilburn, an infectious disease specialist in Vancouver, is one such doctor. Desperate to contain the spread of the new superbug, he joins forces with Lina Lopez as they try to find some way to halt the growing epidemic. What they don't realize is that shadowy forces are conspiring to spread the disease on purpose–and they will stop at nothing to avoid exposure.