Darkness Visible (Darkness Visible #2)

When the demons came, humanity reluctantly learned to share the world with another sentient race. Eighty years later, this uneasy co-existence has spawned an endless terrorist conflict. Detective Daniel Aston, charged with being the thin blue line between the two sides, is tested to the limit when a demon sets up house inside his soul. But to save his daughter, he'll pay any price-including genocide.