"Sudden gains" is a robust phenomenon that has been found to occur among a variety of psychotherapies, clinical conditions, settings, patient populations, and differing levels of therapist expertise. Sudden gains predict superior end-of-treatment outcomes and long-term maintenance of gains. While cognitive changes during the critical session appear to account for the sudden gains, the nature of these changes has not been fully explained, and no detailed reports of how therapists and patients explain these changes have been presented. This case involved a 61-year-old woman with depression, fibromyalgia, and severe osteoarthritis who, after being in psychotherapy treatment for nearly a year, achieved sudden gains after one particular psychotherapy session. The authors discuss the nature of the cognitive changes that both the patient and therapist understood to occur during that critical session and that they believed contributed to the remission of major depressive disorder over a 2-year period. This case study also explores the possible synergistic effects of medications and cognitive interventions on sudden gains. The commentary on the case links this discussion of sudden gains to an intervention created by Viederman and Perry in the 1980s called the psychodynamic life narrative, which they found could sometimes alleviate symptoms rapidly and dramatically by reframing a person's self-image during a depressive crisis, especially one related to a feeling of despair triggered by medical illness. An increased understanding of the nature of interventions that produce cognitive changes leading to immediate, dramatic, and lasting improvement could potentially contribute to the development of more effective treatments for depression and other clinical conditions.