If the therapist's job is the steady provision of a safe, contained therapeutic framework, then breaks and transgressions of those clear and firm boundaries indicate a failure on the therapist's part - a mistake. However, every broken boundary is accompanied by the emergence of precious unconscious material, intensely relevant both to the client's inner world and to the dynamic in the therapeutic relationship. How can we perceive, understand and - most importantly - engage with such threats to the working alliance in a way which it turns 'the mistake' into a transformative deepening of the therapeutic process? Whilst not exactly predictable, neither do disturbing breaks in the boundaries occur out of the blue. There is usually a slow build-up, often noticeable in supervision over a period of weeks, that leads up to the eventual breaking of boundaries. This process happens largely subliminally and for many practitioners, unconsciously. But that does not mean it is necessarily beyond the reach of awareness. We can enhance our perception of the subtle dynamics that lead to boundary breaks by approaching them as relational body/mind processes. There are different kinds of boundaries on mental, emotional, physical and relational levels, with different clients, therapists and character types favouring some levels over others. As these dynamics rely on subliminal and non-verbal communication, we will explore these issues in an embodied, experiential fashion.