A strain of the deadly Marburg virus has come up for sale on the black market, and the seller has showcased the wares by infecting an African village. APO has one potential lead: a researcher named Magrite whose success in treating Marburg victims may be the reason for his sudden disappearance. Out in the field again, Agent Sydney Bristow and her father, Jack, close in on the kidnapper, but determining Magrite's location is only the first challenge in a chain of obstacles. Magrite has a dark secret that forces Sydney to confront her past, even as APO races to stop the distribution of a new and terrifying weapon.