You Only Live Twice (2003)

From the introduction:

The year is 590, 23 August. Rubenz, Ebon Investigator (SCL 6D), chooses steel. His controlled gasp as life leaves his body echoes around the chamber. Only one other hears his last breath in the lower dungeons of the Gothic Cathedral that is known as Dark Lament HQ, Central, Mort. He was a model employee of SLA Industries and had built on his reputation as class investigator to climb the ranks of Operatives before transferring to Internal Affairs. During the last 13 months he fought the dream demons, though eventually they plagued his waking hours. In the end the noise was too much and the drug was seriously affecting his work.