This study adds a phase‐by‐phase perspective to the case of Susan, with the aim of better understanding the processes of change in this therapeutic case. A team of 3 raters integrated the sequential phases of the Paradigmatic Complementarity Metamodel with a moment‐by‐moment tracking method—the Developmental Analysis of Psychotherapy Process method—to analyse this therapeutic process and clarify what happened throughout that may explain phase gains and how the therapist facilitated them. The results suggest that Susan evolved in accordance with the sequence of phases proposed by the Paradigmatic Complementarity Metamodel. We illustrate and explain this with therapeutic interactions representative of Susan's development within the evolving therapeutic process. This case study is the third of a series intended to contribute towards the optimization of clinical decisions in therapeutic processes by identifying markers of phase progression and assessing the value of the therapeutic interventions offered.