Informal carers are increasingly involved in supporting people with severe and enduring mental health problems, and carers' perceptions impact the wellbeing of both parties. However, there is little research on how carers actually make sense of what their loved one is experiencing. Ten carers were interviewed about how they understood a loved one's psychosis. Data were analysed using a hermeneutic-phenomenological approach. Three themes described the carers' effortful quest to understand their loved one's experiences while maintaining their relational bonds. Carers described psychosis as incomprehensible, seeing their loved one as incompatible with the shared world. To overcome this, carers developed hermeneutic 'mooring points', making sense of their loved one's unusual experiences through novel accounts that drew on material or spiritual explanations. The findings suggest that informal carers resist biomedical narratives and develop idiosyncratic understandings of psychosis, in an attempt to maintain relational closeness. We suggest that this process is effortful - it is hermeneutic labour - done in the service of maintaining the caring relationship. Findings imply that services should better acknowledge the bond between carers and care-receivers, and that more relationally oriented approaches should be used to support carers of people experiencing severe mental health problems.