In the early 20th century, Carl Jung, a young and ambitious psychiatrist employed at the Burghölzli Clinic in Zurich, begins treating Sabina Spielrein, a highly intelligent Russian woman with a troubled past and a complex case of hysteria. Jung uses Sigmund Freud's talking cure, an innovative and controversial method at the time, which entails delving into Sabina's repressed emotions and experiences to understand and alleviate her psychological distress. As Sabina begins to recover under Jung's care, she expresses a deep interest in psychoanalysis herself and becomes an adept student, closely observing and learning from Jung's techniques.

Simultaneously, a professional relationship blossoms between Jung and his mentor, Freud, the father of psychoanalysis. The two men engage in extensive correspondence and collaborations, discussing theories and cases, notably Sabina's. Jung's admiration for Freud's work and his desire to innovate within the field create a balance of mutual respect and intellectual curiosity. However, as Jung delves deeper into his exploration of the human psyche, he begins to question some of Freud's methods and theories, setting the stage for theoretical disagreements. These professional tensions, along with the complexities of Jung's therapeutic relationship with Sabina, lead to ethical dilemmas and personal introspection, challenging the boundaries between doctor and patient as well as mentor and protégé.