The following contains plot spoilers – read at your own risk.
New York City, March 3rd, 1896.  John Moore was sitting at the edge of the bed in a fancy room, wearing just a white shirt and partially unbuttoned trousers and watching a woman at her boudoir's dressing table wearing an engagement ring before starting to untie her corset. Once he undressed her entirely, enjoying the sight of her naked body, the two indulged in an erotic embrace with the woman claiming to love another man, asking John to forgive her. The lovemaking was interrupted by the maîtresse of the brothel, a plump middle-aged woman saying a young lad urgently requested Mr. Moore. John hurriedly dressed, leaving a coin in Flora's hand while the young prostitute returned him the engagement ring.
Once outside the brothel, John found himself in front of the young lad, Stevie, sitting in a carriage and stating that "he" needed him. Without hesitation, John let Stevie drive through the nightly and dirty streets of New York, asking for explanations as he tried to drink from his silver flask. The rush to the unknown place was frantic, making John impatient for ignoring what was waiting for him at the end of the trip, knowing only that the police were there, including Commissioner Roosevelt. Once at the Williamsburgh Bridge construction site, John Moore found an initial refusal by the police to let him through. He introduced himself as an illustrator for The New York Times. At the first warning of indifference by the police officers who did not really care about the difference between reporter or illustrator, John lied, asserting that Commissioner Roosevelt was waiting for him.
Having succeeded in his intent, John was escorted by Captain Connor to the scene of the crime, where the lie was soon unmasked by Roosevelt. Therefore, John revealed the real man who had sent him there: Dr. Laszlo Kreizler, the known alienist. His job was to capture an image of the crime scene on Kreizler's behalf. John managed to convince the Commissioner, who consented as long as John thought he could stomach it. The crime scene turned out to be excruciatingly creepy; The battered body of a young boy in a girl's white dress soaked in blood was sprawled on a section of the bridge under construction. The right hand had been severed, the abdomen disemboweled and the eyes plucked out of the eye sockets, probably "eaten by bird or rats" according to Connor. John had a brief discussion with Captain Connor about the scornful terms used against the dead boy. While trying to repress retching, John overheard Captain Connor told Commissioner that the boy's name was Giorgio Santorelli, a "boy-whore"  working at the Paresis Hall. Appealing to all his mental strength, John knelt by the wretched corpse, starting to sketch on his notebook.
The next morning, John headed to the Kreizler Institute to meet with the alienist and longtime friend. Dr. Kreizler greeted John by offering him a glass of cognac in a sitting room near his office, though without being able to quiet the illustrator. In fact, John wanted to know why his friend had caused him to a sleepless night which was very likely going to be the first of many. The doctor explained that he had to resort to such a ploy to bypass the police officers and their politics, apologizing to John for using him. John, then, handled him the drawings that left the doctor dissatisfied with the lack of realism. According to him, the drawings were too idealized, like the Renaissance paintings of a martyred saint rather than a mutilated child. John was not enthusiastic about the criticism, especially when he had to witness such a macabre display for those sketches. Reluctantly, he found himself describing to Dr. Kreizler the more gruesome details about the corpse and how the soft organs and genitals had been violently removed. He poured himself another drink.
Since he could not spell out the reasons Kreizler showed such macabre interest, John suggested if he was going to question the suspect in the murder, finding himself faced with the rare opportunity to leave his friend speechless. The doctor, in fact, was not aware that a man had been indicted for the crime. John, then, decided to go with Kreizler to Bellevue Hospital, where the alienist would question the suspect.
The criminal asylum ward of the hospital was completely different from the welcoming environment of the Kreizler Institute, and John often found himself walking as close as possible to his friend for fear of being attacked by one of the inmates. The suspect, Henry Wolff, was accused of repeatedly stabbing Edwin Band, a friend of his in a fight and since the crimes had taken place in relatively short times and nearby, police officers had promptly linked the two. John stood aside to observe the friend inquiring about the murders with the accused, disturbed by the crises of the various inmates and the wretched physical appearance of Henry Wolff, whose face was horribly disfigured by syphilis. When Wolff turned to him with sexual innuendo after Kreizler mentioned Santorelli working at the Paresis Hall, John was aghast, seeking support in Laszlo. In response, Kreizler decided to enter the cell with the suspect, much to John's distress who was already picturing Wolff killing Laszlo in cold blood.
Left the Bellevue Hospital, John and Laszlo headed to the New York City Police Department, intending to chat with Commissioner Roosevelt about what they had discovered by questioning Wolff and his innocence for the Santorelli murder. Having made their way under the disdainful look of former Commissioner Thomas Byrnes and police officers still loyal to him despite Byrnes being retired at the entrance of the police station, the two friends arrived at the inspector's office where, unfortunately, were stopped by his secretary. John immediately recognized her as Sara Howard, an old family acquaintance through her own parents, but the woman did not seem inclined to favoritism nor to be disrespected in the workplace simply because she was a woman. John tried to dissuade her with the only result to make her more nervous, continuing to refer to her with the first name instead of Miss Howard, a mistake repeatedly corrected by the young secretary. Meanwhile, Laszlo took advantage of their bickering to get into Roosevelt's office. At this point, Moore just stepped inside, followed by Miss Howard, both standing on the threshold while Kreizler and Roosevelt exchanged opinions about the investigations with Kreizler pointing out similarities with a three-year-old unsolved case about the butchering of Benjamin and Sofia Zweig. When the conversation became particularly gory in the details, John hinted to asking Miss Howard to be sent out of the room.
Afterward, John and Laszlo headed out of the police station, where John claimed that Kreizler could be "subtle like a blowtorch, sometimes." Laszlo ignored the statement and inquired about Sara Howard. John remained near the police station until Miss Howard finished her shift, and approached her to ask her to retrieve the file on the Zweig case on Kreizler's behalf only after asking permission to address her as 'Sara,' to which she agreed but exclusively off her official duties. Since Sara proved impassive about the alienist's request, John left her one of his drawings before continuing on his way, hoping that the sight of Santorelli murder pushed the woman to collaborate with them.
Later that evening, John returned to the brothel to spend more time with Flora, repeating the usual roleplaying of the treacherous fiancée. On his way out, John found Sara waiting for him in front of the building. He immediately asked her how did she find him and then, expressed concern about Sara being all alone at night in such an unsavory neighborhood, but the young woman shrewdly replied that no criminal wandering in the neighborhood could be worse than her uncouth colleagues at the police station. She then handed him the Zweig file she "borrowed" for Dr. Kreizler, only asking to be briefed about any news on the matter, to which John agreed.
Shortly after, John headed to Kreizler's house, bringing his friend the documents that, however, turned out to be unusable for their purposes because of how mediocrely the police officers had drawn them.
The following day, John was summoned to the Kreizler Institute, where Dr. Kreizler introduced him to Detective Sergeants Marcus and Lucius Isaacson, charged by Theodore Roosevelt for the autopsy on the bodies of Benjamin and Sofia Zweig at the Kreizler Institute, since the coroner's office was not safe from prying eyes. Since the car would take some time, Laszlo invited John to an earlier dinner but their plans were soon altered by a mysterious envelope left in Kreizler's carriage. The two friends went in pursuit of a man –
possibly the murderer – but reaching no results. Once John had reached his friend in the attic of an unused palace, the alienist handed him the wrapping, revealing a severed tongue inside, and asking John if he remembered any detail about Giorgio Santorelli's mouth.
A few days later, John had returned to his daily routine, sketching portraits for rich and pretentious members of high society. In Mrs. Tinker's living room, John was portraying her daughter, Charlotte but he was advised by Mrs. Tinker to correct the drawing since, in her opinion, he had not quite captured the line of her jaw.
Back home, John met Sara Howard standing in front of his house's front door. The woman was willing to visit the Santorelli because of a bad presentiment gave to her by Captain Connor, and intending to understand the situation more clearly. John tried to dissuade her but when she teased his pride questioning his courage, John agreed to accompany her even though he was not entirely convinced of getting something done in visiting the victim's parents.
Once in Little Italy thanks to a ride by carriage by Cyrus Montrose, John and Sara entered the dilapidated building overcrowded by Italian immigrants. In the dark, dirty and rat-infested stairways, John tried to dissuade Sara from picking up an infant from the ground, since he could have some disease. The woman did not listen to John's concern but had to return the child to the wretched mother who reclaimed it. Found the apartment where the Santorelli lived, the two of them were invited to enter by a boy – who later they discovered to be Enzo, Giorgio's brother – and John was mistaken for the doctor by Mrs. Santorelli, who had sent a picciriddu (children) to look for a doctor to alleviate her husband's suffering. Cleansing Mr. Santorelli's wounds with a bit of alcohol after Sara had urged him to pretend to be a doctor, the woman asked Mrs. Santorelli and Enzo what had happened. The two friends discovered, then, that two policemen and a priest had visited the Santorelli, threatening to keep their mouths shut and that besides Giorgio and Zweig twins, there were other victims.
Later, John investigated on his own, and briefed Sara and Laszlo during a meeting at Kreizler's house. Browsing old articles at The Herald, John had discovered that Aaron Morton, one of the victims, worked at a brothel called Shang Draper's, and had been found dead near Brooklyn Bridge a month earlier. Since there were no close relatives, his body had been buried in the Potter's Field mass grave. When Kreizler asked about the family situation of Giorgio, John said that he was beaten like all the other children in that neighborhood and that he was avoided by the other children, because they found Giorgio to be "in some manner effete or, well, inclined toward contrary sexual instinct." Kreizler became exceedingly upset, as this meant little or nothing, and Giorgio's sexual nature was too vague to give rise to conjecture.
John was invited by Kreizler to spend the evening together, and they both wore very elegant clothes. On board the carriage, Kreizler inquired about Miss Howard and John recounted some of his friend's sad past; her mother died when she was young and her father died during a hunting accident, or at least this was the official version. The rumors were that he had killed himself. Heartbroken with grief, Sara was sent to a sanatorium. John then found himself denying Laszlo's insinuations of a love interest in Sara.
At the Opera House, John struggled to pay attention, falling asleep until the interlude after a brief conversation with Laszlo about Theodore Roosevelt and other members of high society, such as Mayor Strong or J.P. Morgan. Once outside in the hall, John took a glass of champagne each, but he drank them both when Laszlo refused his own. He silently backed Kreizler while he argued with Roosevelt, imposing his presence in the investigation and informing the commissioner of his intention in pursuing a parallel investigation, with Miss Howard acting as a liaison between the two of them.
The two friends then headed to Delmonico's, where they met with Sara and the Detective Sergeants Marcus and Lucius Isaacson. During dinner, the two detectives exposed their recent discoveries; first of all, they showed the ensemble an Arkansas Toothpick, a dagger they considered to be of the same type as that used by the murderer. John was stunned, but Sara scolded him, saying that she could very well hear everything there was to say. The detectives, then, went on to illustrate their theory on Dactyloscopy, showing both a machine equipped with magnifying glasses to show their own fingerprints to give a practical example of their theories and a timepiece found in Benjamin Zweig's burial suit, bearing a bloody finger-mark probably left by the murderer.
At dinner ended, John argued with Laszlo because of the intention of the latter to want to involve Sara in his manhunt. While Sara and Laszlo were returning home aboard the caleche, John said he wanted to walk home, ignoring Sara's concern and telling her that he was not a child.
Angered due to the conversation with Laszlo, John wanted to test his contribution to the investigation and went to the Paresis Hall after wandering the streets crowded with prostitutes, gamblers, and street vendors. John found himself immediately surrounded by uninhibited boys wearing succinct female corsets and petticoats and a large number of clients, respectable men of society looking for sexual favors from the boys. Rejecting the advances of some of the boys, John asked questions about Giorgio Santorelli to the bartender, who advised him to mind his own business. John insisted, saying that the other boys could be the next victims and the man, flirting with him, took advantage of a moment of distraction to drug John's drink. John was then approached by a mulatto boy who introduced himself as Sally, who led John into one of the upstairs rooms.
John offered Sally some money in exchange for information about Giorgio, and Sally said he called himself Gloria around there. John began to show symptoms of poisoning caused by the drug, struggling to breathe and slumping on the bed. As his vision blurred, a couple of boys assaulted him under the eyes of Biff Ellison, the bartender who had drugged him and two other men, Paul Kelly and Captain Connor, who identified John as a friend of Roosevelt and Kreizler. 
John woke up drenched in sweat in the battered bedroom of the brothel where he saw Sally standing in front of the window in a dressing gown, her back to him. When John called her, the young prostitute turned to reveal the same wounds on Giorgio Santorelli, such as empty orbits and blood-covered face. John suddenly woke up from the nightmare, finding himself lying on a sofa in Dr. Laszlo Kreizler's library with all his colleagues in the middle of their duties. Laszlo immediately rushed to ask him how he felt, saying that young Stevie had found him wandering in an alley down in the Tenderloin. Sara added that he was missing his trousers while handling them to him and while John tried to cover the bare legs with a blanket, overwhelmed by embarrassment, Marcus Isaacson stated that it could happen even to be the best of them. John drank the glass of water that Laszlo had offered him, asking in vain to have something a little stronger. John then began to look around, realizing that he was not in Laszlo's library, but in what Laszlo defined a safe place from prying eyes and ears. Laszlo continued to ask John where he had been and what he had discovered at the Paresis Hall while John tried to recover from his hangover. Still quite dazed, he began to remember what had happened, telling how he had met Sally, one of Giorgio's friends and that "Gloria" was well-liked, especially among the wealthier clients. Sara proposed that perhaps this was the reason why the police put pressure on Santorelli family, to avoid scandal. As John tried to remember, however, he found himself under the accusing gaze of his colleagues, hastening to make it clear that he hadn't had sex with any of the Paresis Hall boys. Annoyed, he wrapped the blanket around his waist and left the room.
Back home, John was greeted by his grandmother, who expressed concernment for her grandson's behavior. John snorted, not at all enticed by the fact that she had talked to his father or the prospect of taking part in a meeting with a potential fiancee planned by his grandmother for that afternoon.
In the afternoon, Mrs. Abigail Bell visited with her daughter Caroline carrying on a conversation based entirely on small talk, much to John's boredom. Mrs. Bell mentioned John's lost brother, drowned years ago, and Caroline hastened to say that she was frightened by the sea. Addressing her as Madeline, John stated that the sea was innocent and that the fault was not rough seas so much as an unsteady sailor. The conversation then came to an awkward deadlock.
The next morning, John woke up dazed and immediately poured a glass of liquor, toasting in the direction of a drawing of his late brother hanging on the wall of his room. Still sleepy, he noticed a little bird on the window sill and immediately remembered an essential detail discovered during his visit to the Paresis Hall.
John then rushed to the Kreizler Institute to brief Laszlo about it. Sally had mentioned that Giorgio had not left his room and that when they broke the lock they found an empty room. John remembered a window, from which Giorgio had flown away according to Sally and, moreover, one of the wealthy clients with a "silver smile" had been at the brothel that night. Laszlo replied that they were nothing but ravings with no use and that he needed to speak directly with Sally.
In the evening, John and Laszlo went to the Tenderloin where they were able to talk to Sally in a dark alley where Laszlo came to the conclusion that the murderer was supposed to be someone whose victims trusted so much to follow him anywhere without too many questions.
In the middle of the night, John and Sara were led by Cyrus and Stevie to the old immigration station, which was about to be modernized as an aquarium. Another child had been butchered, and his body abandoned on the glass ceiling of the building. After reaching the rest of the team on the roof, John began sketching the body for later evaluations, offering his support to Sara when she was dizzy at the sight of the butchered body. Having to leave the crime scene due to the arrival of Captain Connor and his policemen, the team had to flee secretly and John inadvertently dropped his sketchbook during their flight.
The next morning, John and Sara had a meeting with Kreizler in his house, where they had a heated argument with the alienist. John, in fact, was deeply irritated by his friend's insinuations, stating that despite his reckless behaviors, he did not go around butchering children and found it difficult to empathize with the murderer.
On the caleche, John apologized to Sara for revealing to Laszlo about her past, but the woman said she understood in part what Kreizler had tried to say. John stood firm in his belief that Laszlo had been very impertinent. When Sarah asked about Mary Palmer, Kreizler's housekeeper, John revealed that she had been taken under the protective wing of Kreizler after she had burned her father to death. Sara began to formulate assumptions about the relationship between Mary and Kreizler, prompting John to tell her that she was becoming like Kreizler; That both of them were doing it. Sara replied that John could be quite amusing when he wanted, and John kissed her on the cheek. At home, John realized he had lost the sketchbook.
John Schuyler Moore is a handsome man in his thirties with an athletic built, broad shoulders, light blue eyes, black graying hair, and fair complexion. A member of the upper middle class, John wears very elegant and refined clothes, accompanied by accessories such as hats, precious rings and tie-pins, silver pocket watch, and cufflinks. His suits are often in shades of blue, matching his eyes and complexion. The external beauty, however, hides a profound inner sadness that has afflicted John's on a very intimate level, making John a slave to different vices – drinking and frequenting prostitutes regularly. According to his close friend, Dr. Laszlo Kreizler, John exploits vices to avoid facing his problems. When not drunk, John has proven to have a kind and caring soul, almost fragile facing of the macabre and horror of a deviant mind, summed to the uneasiness in finding out the squalid lives of the lower classes. His sensitive soul is clearly visible in his artistic flair and in the creativity with which he manages to capture details in his portraits. In order to prove to himself and to his close friends to be a better person, John quitted drinking and visiting prostitutes with the result of having light tremors in his hand.