Catherine is an energetic young mother living in a house connected to her husband's operating theater. She experiences deep feelings of failure and isolation because she cannot produce enough breastmilk to feed her newborn daughter. Curious and highly expressive, she refuses to censor her emotions in a polite society that expects her to remain quietly devoted. Her desire for genuine intimacy drives her to investigate the mysterious electrical treatments happening in the next room.

Dr. Givings is a practical, science-minded gynecological physician who prides himself on his dispassionate professionalism. He treats women diagnosed with hysteria using his new medical invention: the electric vibrator. He believes fully in the cold logic of medicine and electricity, keeping his clinical work completely separated from his domestic life. This strict separation often causes him to ignore or dismiss his wife's obvious emotional distress.

Sabrina arrives at the doctor's office as a fragile, anxious woman plagued by unexplained fatigue. Diagnosed with hysteria by Dr. Givings, she suffers from the quiet sorrow of being unable to conceive children within a passionless marriage. Through her daily electrical treatments, she slowly sheds her polite timidness, regaining her energy and discovering repressed physical desires.

Elizabeth is a Black housekeeper working for the Daldrys. After losing her infant son Henry Douglas to cholera, she is offered up by Mr. Daldry to serve as a wet nurse for Catherine's baby. She carries a profound, silent grief for her child while performing the deeply intimate and physically taxing job of feeding another woman's daughter. Her presence forces the other characters to confront the physical realities of motherhood and human connection.

Mr. Daldry is Sabrina's brusque and highly traditional husband. He feels frustrated by his wife's declining energy and emotional sorrow, preferring to remember the vibrant seventeen-year-old girl he originally married. He is largely oblivious to the actual emotional needs of the women around him and regularly misinterprets the natural exuberance of others as romantic availability.

Annie is the intelligent, stoic midwife who assists Dr. Givings in his operating theater. She maintains a highly professional demeanor while manually or electrically bringing female patients to orgasm as part of their medical treatment. Despite her quiet exterior, she reads ancient Greek philosophy and harbors her own complex desires, revealing an unexpected depth beneath her clinical duties.

Leo is a passionate, highly dramatic artist seeking treatment from Dr. Givings as a rare male patient diagnosed with hysteria. He despises modern inventions like electricity, vastly preferring the romance of sunsets and candlelight. After a romantic rejection leaves him physically weak, he projects his artistic ideals onto the women he meets, often viewing them as muses rather than complete individuals.

Lotty is Catherine and Dr. Givings' infant daughter. Her simple physical need for milk initiates the primary conflict in her mother's life and necessitates hiring Elizabeth as a wet nurse.