A construction project beneath the National Mall unearths a terrifying secret dating back to the Civil War. It is a cache of bones preserved in amber and buried more than a century ago by a cabal of scientists to protect humankind. The scientists, led by Alexander Graham Bell, who helped found the Smithsonian Institution, were safeguarding a wonder like no other: the very secret of life after death. But this prize is linked to a horror from the ancient past, a horror that has remained dormant yet all too frighteningly alive in the marrow of those bones—and has now been freed again to wreak havoc on an unsuspecting world.

From a crystalline lab atop Mount Fuji to a verdant island off of Hawaii teeming with the “dark matter of life,” Sigma Force must unlock a deadly mystery that winds back eons, to the very origins of life on Earth. But with each discovery Sigma Force makes, the menace they hunt is spreading, changing, growing, adapting—surviving every attempt to stop it from reconquering a world it once ruled.

With time running out, Commander Grayson Pierce will be forced to make an impossible choice. To eradicate this ancient threat and save humankind’s future he will have to team up with Sigma’s greatest enemy—the newly resurrected Guild—even it if means sacrificing one of his own.