Fresh from their conquest of Chondax and the discovery of Horus's rebellion, Jaghatai Khan's warriors stand divided. Long considered one of the less trustworthy Legions, many of the White Scars claim to owe their loyalty exclusively to Terra, and others still to the Warmaster and his warrior lodges. But when a distress call from Leman Russ of the Space Wolves brings the wrath of the Alpha Legion to Chondax, the Khan's hand is forced and the decision must be made - in the great war for the Imperium, will he side with the Emperor or Horus?