Dr. John Felder is a forensic psychiatry consultant for the New York Department of Health. He took a particular interest in Constance Greene while working on her case during the events of the Helen Trilogy, and is one of the few who know Constance's true history.
Felder is described as small and slender, with short mouse-colored hair and a trim Van Dyke beard. He works as a consultant with the New York Department of Health, usually on cases involving involuntary commitment.When Constance Greene was taken into custody upon her return to the United States for the murder of her infant son, her case was given to Felder, who determined she was mentally unfit to stand trial. She was committed involuntarily to the Bedford Hills Correctional Facility indefinitely, but following a meeting with Special Agent Pendergast, Felder agreed to have Greene transferred to the Mount Mercy Hospital for the Criminally Insane, filling the vacancy left by the recently deceased Cornelia Delamere Pendergast.
Felder himself, however, was both fascinated and unnerved by Greene's incredible story, and he soon found himself researching the young woman's claimed history. Acting on Greene's testimony from her commitment hearing — where she claimed the records in the city archives would corroborate her 1870s birth — Felder launched an exhaustive search through the archives of the New York Public Library that yielded only one official record mentioning Constance Greene: the 1874 census. Disheartened, he began leafing aimlessly through some late 1870s newspapers when he discovered an 1879 copperplate engraving called Guttersnipes at Play. The engraving featured a group of street urchins playing in front of a row of tenements, while off to the side stood a young girl who was almost a photographic likeness of Constance Greene.Felder continued to meet with Greene over the coming weeks. On the morning of her transfer to Mount Mercy, the New York Times ran a story about the discovery of a journal from the early 1880s containing the only known detailed neighborhood map in existence of the area around Water Street — where Greene claimed to have been born — in the 1870s. Sensing an opportunity to break through her elaborate fantasy, Felder quizzed Greene about her childhood neighborhood, and was stunned to find that her vivid descriptions matched the historical map precisely, despite confirming that she had not had access to that morning's Times.
Unfortunately, Felder's earnest naiveté cost him dearly when Judson Esterhazy — masquerading as one of Greene's previous psychiatrists — successfully tricked him into a private audience with her, during which Esterhazy persuaded her that Pendergast needed her help and concocted an escape plan. Esterhazy convinced Felder to authorize an excursion to the New York Zoo, where he kidnapped Greene to lure Pendergast into a trap aboard the Covenant yacht Vergeltung.Felder avoided further professional disgrace upon Greene's safe return to Mount Mercy, but not without a severe dressing down by Pendergast, the mayor of New York, and even the real Dr. Poole, whom Esterhazy had impersonated. The worst, however, was a withering rebuke from Greene herself, who effectively fired him as her treating psychiatrist, although she acquiesced to allowing him to continue to visit as an acquaintance.
In spite of himself, Felder began to believe her story. He showed Greene the Guttersnipes at Play engraving, and she wistfully described its origin: the artist, Alexander Wintour, had been illustrating a series of articles on the New York tenement districts. After sketching Guttersnipes at Play, he had asked to paint her portrait for his portfolio, providing the pencil sketches for the portrait by way of payment. Her older sister, Mary, gave him a lock of Constance's hair in return in gratitude, a common practice at the time. She recalled Wintour placing the lock into a small envelope and pasting it to the inside of his portfolio cover, and suggested to Felder that if the portfolio were to be found with the lock still existent, a simple DNA test would prove her story.
Felder traced Wintour's history to Southport, Connecticut, and ultimately retrieved the lock at great peril from Wintour's estate, which was guarded fiercely by the artist's grandniece. He returned it to Greene, along with the sealed results of a DNA test, and admitted his growing feelings for her, which she graciously accepted but could not return. instead, in the strictest confidence, she told him her full story, leaving out only the nature of Enoch Leng's true research.