City of Night. It was co-authored by Koontz and Ed Gorman. The story picks up immediately after the end of the first book, Prodigal Son. There we learned about what the 240+ year old Dr. Frankenstein, aka respected New Orleans business man Victor Helios, has been up to in his laboratory. The good doctor has been developing, apparently with great success, a race of life forms who appear and act like normal members of society. However, these creations of the new race are superior to God's old race in terms of strength, intellect, reflexes, healing powers, longevity, and immunity to pain and disease. They have been bred as slaves and placed throughout the New Orleans community in positions of government, the police force, the church, and a host of various other jobs. They are all waiting until their numbers are sufficient for Dr. Frankenstein to give the command to eliminate the old in favor of the new, with Frankenstein as their god and ultimate authority.
The trouble is that though these creations were genetically engineered to live for a millennium, greater and greater numbers of them are losing their way. Though they were not designed to feel love or hope or to seek a purpose other than to fulfill their roles, many are suddenly breaking down. Somehow they have developed acute mental symptoms stemming from their soulless nature. Others seem to suddenly go insane, lose their minds, or forget their purpose. Some self-destruct, others suddenly desire nothing but to destroy everyone they see. While Frankenstein seems to be fiddling, his Rome, unbeknownst to him, is beginning to burn.
With this backdrop, New Orleans detectives Carson O'Connor and Michael Maddison have come to understand what they are up against. With a pair of Frankenstein's assassins on their heels, they are trying to develop a plan to stay alive long enough to put an end to Frankenstein and his army of nearly unstoppable mutants. Their only ally is Deucalion, Frankenstein's first creation, who has powers that his creator did not intend and does not understand. Yet Deucalion's programming will not allow him to harm his creator. The situation in New Orleans has reached the boiling point. Worse, we have just learned that Frankenstein has constructed two new high capacity farms for creating his armies that are nearly ready to go online. The situation seems hopeless. Now onto the next part of the story, Dead and Alive.