Captain Cato Sicarius leads his Ultramarines brothers in an assault on the space hulk Final Liberation to destroy the Genestealers holed up there. Vowing to carry out the operation according to the rules of the Codex Astartes and determined to shed his reputation as a renegade from tradition, Sicarius carries out the mission admirably - until something unplanned begins to happen when First Captain Severus Agemman unexpectedly puts the lives of his brethren at risk.