Investigating the silence of a distant star fort, the Imperial Fists are attacked by the monstrous tyranids. With their ship in danger, the Space Marines enact a dangerous boarding action into the heart of the xenos bioship, seeking to rip the heart from the aliens and save the world below. Usually, its hordes of tyranids that invade humanity's Space Hulks - well now the tables have turned. It's Space Marine against xenos monster in the depths of space - will the Imperial Fists succeed in their mission to destroy the hive ship, or have they just volunteered themselves as appetiser for the forthcoming invasion?