If Sek's covert operations are brought to light, it will shatter the uneasy alliance between Sek and Gaur, sparking an internal feud that will tip the balance of the Sabbat Worlds Crusade in the favour of the Imperium. The Tanith First – reinforced with additional troops drawn from Verghast and Belladon – and a trio of veteran Space Marines are sent to neutralise the facility at "Salvation's Reach" and gather as much intelligence as possible before they destroy it. However, Gaunt must also see to the protection of the incarcerated Mabbon, deal with the malcontents within the Tanith First, and cope with personal issues that he never anticipated.