When a Deathwatch mission goes awry, a kill-team led by Techmarine Zaeus are forced into a rapid and desperate exfiltration. Their captain, Polino, is badly injured. When they find their transport destroyed, its pilot dead, they know they are in trouble. Hope lies in the chance discovery of a communication from another Adeptus Astartes force on the world and the promise of reinforcement. As his brothers try to hold out against murderous alien kroot, Zaeus goes on alone to find the source of the message and bring help before it's too late.