Seclusion continues to be used in the care of acutely disturbed psychiatric patients despite often emotionally charged debate about its appropriateness within mental health services. Powerful legal and moral arguments about the use of seclusion emphasize an urgent need to critically examine its role in the care of mentally ill people. This paper examines the use of seclusion on psychiatric departments in the management of acutely disturbed patients: 36 psychiatric nurses working in 6 departments in a specialized hospital (the CHS de la Savoie, in Chambery) were interviewed in relation to their perceptions of the role of seclusion. Data were analysed using grounded theory methodology revealing the core conceptual category "controlling" and two sub-categories "watching out for" and "watching over". Seclusion was found to be used as an adjunctive treatment in the care of individuals considered to be "out of control". Clinicians expressed comfort with the use of seclusion, citing a strict protocol that provided parameters for its use. While expert therapeutic interventions were described by clinicians, they are contextualized within a framework of power and control--a framework that stands in stark contrast to contemporary philosophies of nursing care, providing impetus for a reconsideration of the use of constraining practices in the care of mentally ill people.