The series' main character is the psychologist Dr. Laszlo Kreizler, who is assisted in his adventures by reporter John Schuyler Moore, policewoman Sara Howard and Stevie 'Stevepipe' Taggart.
The next book in the series Surrender, New York is set in 2016, but the main protagonist, Dr. Trajan Jones, is also a criminal psychologist, and is the world's leading expert on the life and work of Dr. Laszlo Kreizler.
The sequel was to be set 18 years after The Angel of Darkness, in 1915 New York City, and was to be “centered on nativist violence and terrorism during America’s involvement in World War I".
The second book, a prequel, was to be called The Strange Case of Miss Sarah X, and would have seen a youthful Kreizler, after finishing his psychology training at Harvard, fall under the spell of William James, have his first run-in with Roosevelt, and delve into the secret life of Sara Howard.
It was also announced that the season 1 True Detective director Cary Fukunaga would be brought on board to direct all the episodes and act as an executive producer.