The article explores the telling of co-narrated atrocity stories in accomplishing professional identity. Building on previous work, it is argued that group membership is a prerequisite for such stories to be told. Extracts from empirical data from interviews with social work approved mental health professionals are analysed using an ethnomethodological approach. The findings show how atrocity stories can be co-narrated, not only by longstanding colleagues, but also by two unacquainted persons who share the same professional identity. The article concludes that the ethnomethodological concepts of vulgar competency, unique adequacy, indexicality and the documentary method of interpretation are key to understanding the accomplishment of co-narrated atrocity stories.