One year after the coming of the Emperor to Barbarus, Mortarion and his Legion – the newly renamed Death Guard – have yet to strike out and join the Great Crusade. The primarch is wracked with doubts about his place in this Imperium of Man, and still angry that the Emperor robbed him of his vengeance against the alien father who raised and tortured him. When he is summoned to attend the Emperor on his flagship, will his resentment spill out and threaten the relationship between them? Or will the Deathlord master his emotions and embrace the Emperor's light?