Extinction Darkness: The Extinction Cycle: Dark Age, Book 4 (Unabridged‪)‬

Darkness descends over the survivors of the Extinction Cycle....

With nowhere left to run, the Allied States fortifies their few remaining outposts and relocates Central Command to prepare for their final stand. President Jan Ringgold and her generals know beating the enemy on the battlefield is impossible. The only path to victory seems to be taking down the leader of the New Gods, a sinister Chimera known as the Prophet, before he can complete his campaign to enslave humanity. 

While Captain Reed Beckham trains new troops, his wife Doctor Kate Lovato returns to the tunnels to infiltrate the bioengineered enemy communication network. Injured and exhausted, Master Sergeant Fitzpatrick and Team Ghost make their way back from Canada with a Chimera prisoner that might be the key to finding the Prophet and raising a new army. 

In this thrilling conclusion to the Extinction Cycle series, humanity bands together one last time against the Variants. But time has run out for the heroes of the first war to save what remains of the Allied States and, perhaps, the world.