For the Emperor
Ciaphas Cain
Commissar Ciaphas Cain must whip a regiment into shape and reinforce a distant planet the Tau are looking to annex. But there's more going on than meets the eye, and Cain is conscripted by an Inquisitor to solve a larger--and deadlier--problem.
Spoiler
The planet has been invaded--for several generations, apparently--by Tyranid genestealers. Cain gets away fine, and the planet will be cleansed of the infestation, but they allow a few of the genestealers to get away with the departing Tau, so as to sow discord among their enemies.