A military research station buried in the remote Sierra Nevada Mountains 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 help arrives to investigate, they discover that everyone is dead--not just the scientists, but every living thing for fifty square miles is annihilated--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. The dead scientists were working on a secret project, researching radically different forms of life on Earth, life that could change our understanding of biology and humanity itself. But something set off an explosion in the lab, and now Sigma must contend with the apocalyptic aftermath.

Following a fascinating trail of clues, Sigma will make a shocking discovery involving a prehistoric continent and a new form of life and death buried under miles of ice. Gray Pierce and his dedicated team must race to decipher millennia-old secrets out of the frozen past and untangle mysteries buried deep in the darkest jungles of today, as they face their greatest challenge yet: stopping the Sixth Extinction--the end of humankind.