Organisations, like people, develop through processes of increasing differentiation and integration as they come into contact with challenges from the internal and external world. Certain challenges—for particular missions— can lead to derailments of organisational development. Given the central boundary function of the mission, its character and shape can serve as a lens through which to grasp organisational vulnerabilities. This paper reviews the impact of two organisational consultations, a decade apart, on the development of a psychiatric treatment centre. The centre's mission, shaped by engagement with the outside world, served as a lens through which to grasp and repair systemic organisational dysfunction.