When the ‘unexpected’ happens to a group conductor, it can be disturbing but it can also provide an excellent learning opportunity. This article explores the response of a therapy group to an unexpected event—one that had an impact on containment—and looks at what can be learnt from a theoretical perspective. A musical analogy is used to highlight the power of the ‘expected unexpected’ and there is a focus on the issue of pattern recognition as it arises in both music and psychotherapy. This leads to a consideration of ideas about change from writers such as Zinkin, Stacey and Garland. Bringing these theories together with Foulkes’ group specific factors of resonance and location, I argue that the ‘unexpected’ is a crucial and perhaps necessary element for change in an analytic group.