A military research station buried in the remote Sierra Nevada Mountains of Northern California broadcasts a frantic distress call that ends with a chilling order: "There's been a breach. Failsafe initiated. No matter the outcome: kill us... kill us all." When park ranger Jenna Beck arrives with her search-and-rescue dog, Nikko, to investigate, she discovers that all of the scientists in the lab are dead and every living thing for fifty square miles is annihilated: animals, plants, insects, even bacteria. The land is completely sterile - and the blight is spreading. Only one team on earth has the scientific knowledge and military precision to handle this mission: Commander Gray Pierce and Sigma. As Pierce and his team race to decipher millennia-old secrets, they face their greatest challenge yet: stopping the sixth extinction - the end of humankind.