In the jungles of Aztlan a deadly war of the shadows is being fought. And the Imperial Guard are losing. The alien t’au, though few in number, greatly outclass the soldiers of the Imperium and are taking a serious toll on their forces.

A call for aid is answered by the fearsome Mortifactors Chapter, who come to the world full of grim purpose. Adoni, an unblooded neophyte yet to earn his place, is amongst the war party. As the Mortifactors descend into the jungle vastness, they hunt for a killer, one that will not die easily but that whom Adoni must slay if he is to become part of the Chapter and a Taker of Heads.