A brilliant but relatively unknown philosopher at the time of the novel, who suffers from a variety of illnesses and is introduced to Dr. Breuer for assistance, leading to a dynamic interaction between them.

A fiercely independent woman who propels the novel's plot by persuading Breuer to see Nietzsche and is involved in a notable past relationship with him, demonstrating her complexity and defiance of societal norms.

Josef Breuer's wife, who comes from a wealthy family, is Jewish, and experiences strain in her marriage due to her husband's obsessive work habits and the suspicion of infidelity.

A young 29-year-old aspiring research scientist and mentee of Breuer who forms a close professional and personal relationship with him, and assists in the development of early theories related to psychoanalysis.

A patient treated by Breuer with the "talking cure" for her hysteria, whose condition and interactions deeply affect Breuer’s personal and professional life, coupled with broader themes of societal perceptions of women.