The Fires of Atlantis: Purge of Babylon, Volume 4 (Unabridged‪)‬

Separated, but not out of the fight. Gaby has been captured by a familiar figure from her past. Some might take captivity lying down, but they aren't Gaby. Will and Danny are close on Gaby's trail, but their rescue mission is detoured in a city under siege by a very dangerous new breed of ghouls. The reunited ex-Army Rangers will face their toughest fight yet if they want to get out alive.

Back on Song Island, Lara prepares for an impending attack. She receives unexpected assistance from a man named Keo, an ex-mercenary with his own agenda. Meanwhile, the survivors' radio broadcast has elicited surprising responses from around the globe. It might be the start of a resistance against the ghoul domination, if Lara can keep everyone alive long enough. Where the purge begins, the gates hold, and the stones crumble, the fires will burn.