This paper makes an original contribution through the revitalisation, refinement and exemplification of the idea of the 'critical juncture'. In the health and illness context a critical juncture is a temporally bounded sequence of events and interactions which alters, significantly and in a lasting way, both the experience of the person most directly affected and the caring work which is done. It is a punctuating moment initiating or embedded within a longer trajectory and is characterised by uncertainty. As contingencies come to the fore individual actions have a higher-than-usual chance of affecting future, enduring, arrangements. These ideas we illustrate with detailed qualitative data relating to one individual's journey through an interconnected system of mental health care. We then draw on observations made in a second study, concerned with the improvement of mental health services, to show how micro-level critical junctures can be purposefully used to introduce instability at the meso-level in the pursuit of larger organisational change. In addition to demonstrating why scholars and practitioners should pay closer attention to understanding and responding to critical junctures we are, therefore, also able to demonstrate how their emergence and impact can be examined vertically, as well as horizontally.