This article presents a single-case experimental study of a woman suffering a traumatized reaction to a road traffic accident (RTA). In addition to meeting the DSM-IV (APA, 1994) criteria for the diagnosis of PTSD, the client suffered recurrent bizarre nightmares. The client reported at assessment, that each night her dreams were dominated by a terrifying hooded cloaked faceless figure. The central aim of the study therefore was to assess the efficacy of a psychodynamic-interpersonal (PI) style psychotherapy in the context of an unusual PTSD reaction. The methodology employed an A/B multiple baseline time series design, with six month follow-up. A and B represent a series of dream diary observations under two conditions: assessment/baseline (A) and treatment/intervention (B). Treatment consisted of a manualized psychodynamic-interpersonal (PI) psychotherapy to facilitate insight into the content and meaning of the nightmares. The intervention reduced the frequency and associated distress of the nightmares to zero. Follow-up at six months noted the long-term efficacy of the psychotherapy. The study is discussed with reference to the assimilation model of psychotherapeutic change.