Borealis Four has fallen under the sway of an insidious Chaos cult and its dense jungle terrain make it the ideal battlefield for Straken and his platoon. After a particularly fierce firefight, the Catachans find themselves cut off from the rest of the Imperium forces and must seek refuge in a native village.
Before long, troopers begin to hallucinate and warp-born horrorslay siege to the village. Even Straken himself falls under the sway of the Dark Powers. Can he break the psychic grip in time to save his men or will Borealis Four be Straken's last stand?