|“||"In my experience, the man who enjoys defiling women is usually dominated in his daily life, while the man who is being beaten is probably a bully. Take yourself. With all your intelligence, you're most likely aroused by someone for whom that intelligence means nothing.||”|
|— Mrs. Williams to Dr. Kreizler[src]|
Mrs. Williams is a former patient of Dr. Laszlo Kreizler to whom the alienist refers to discover patterns of deviant behavior.
Mrs. Williams is a former patient of Dr. Laszlo Kreizler who suffers from unspecified mental issues that push her to sadistic behaviour towards those whom both Kreizler and herself have described as "hapless." Mrs. Williams has found a way to perform her impulses through the role of dominatrix during sexual role-playing games. 
Dr. Laszlo Kreizler paid a visit to Mrs. Williams, a former patient of his in order to recollect information on what could drive a man to seek pleasure in the murder. After a man dressed as a housemaid had served tea, Mrs. Williams told him that the man was a foreman at the brewery quite used to giving orders but at her house, he prefers taking them.
Kreizler listened Mrs. Williams telling him how she had passed the stage where she tortured hapless creatures. Since she seemed to be familiar with inflicting pain, Kreizler considered asking for her help to understand the motivations behind it. The woman showed him some butterflies on a frame, stating that beneath their beautiful wings is a whole array of instruments used to inflict agony during the coitus. She went on, saying that the connection between pain and pleasure is far more common than Kreizler thought and that the mind is the most erotic organ of the body.
The alienist asked for further examples given that he wasn't able to grasp the motivation, and Mrs. Williams explained to him that, in her experience, the man who enjoys defiling women is usually dominated in his daily life, while the man who is being beaten is probably a bully. She then made Kreizler uncomfortable when she affirmed that with all his intelligence, he was most likely aroused by someone for whom that intelligence means nothing. Kreizler, therefore, came to the conclusion that the murderer was attracted by his opposite but Mrs. Williams offered another point of view by asking the alienist which of all the stories she told him when she was his patient wormed their way into his mind. Kreizler revealed they were her accounts of men's vulnerabilities in particular interesting, in which he recognized his own weakness, aroused by them. Therefore, that meant that if the murderer enjoys inflicting wounds, there's a good chance he has wounds of his own. Kreizler promptly left the room when Mrs. Williams started to touch his right arm, whispering in his ear that "the cripple in him is looking for the cripple in another." 
Appearance and PersonalityEdit
Mrs. Williams is a young woman in her prime. She has a slim but voluptuous silhouette, a pale complexion, and blue eyes. Mrs. Williams has long mahogany hair styled in an elegant bun. Her dresses are refinedly sewn gowns in dark colors, highlighting her fair complexion. To complete the appearance of the Dark Lady, ruby lips and a pair of blood-colored earrings.
Although she has been in therapy with Dr. Kreizler for a long time, she states that she is no longer subjected to her impulses but that, on the contrary, she has succeeded in dominating them and venting her violent desires through the domination of men in erotic games. Mrs. Williams proved to be in full control of her physical and mental faculties. Besides having an extensive knowledge of carnal pleasures, she is an expert in torture. Her condition, then, has enabled her to better understand the deviant psyche of those who are alienated from reality; for example, the murderer that Dr. Kreizler is desperately trying to stop. The dominatrix is, therefore, pleasantly aware of her persuasive power, and of the effects that she arouses in her subject such as, for example, the rude man wearing housemaid clothes. In addition, her charm is irresistible even for men like Dr. Kreizler.
- Mrs. Williams (about crossdresser maid): "He's a foreman at the brewery. Quite used to giving orders. In here, he prefers taking them."
- Mrs. Williams (to Dr. Kreizler): "I've moved on from torturing helpless creatures."
- Mrs. Williams: "You see these butterflies? Beneath their beautiful wings is a whole array of instruments used to inflict agony during coitus. The connection between pain and pleasure is far more common than you think."
- Mrs. Williams: "Of all the stories I told you when I was your patient, which ones wormed their way into your mind, kept you up at night?"
- Mrs. Williams: "If your friend enjoys inflicting wounds, there's a good chance he has wounds of his own."
- Mrs. Williams doesn't feature in Caleb Carr's novel.
- Ep. 4: These Bloody Thoughts