This article is about the use of qualitative methods in the design and development of new ways of intervening to help children who have been sexually abused. Specifically, it is about ways of including non-abusing parents and carers constructively in the intervention; about the complex, triangular relationships between social workers, children and parents that result; and about the contribution of qualitative methods to the design and development of such interventions. The difficulties of defining a precise model of intervention are discussed. But despite these difficulties, this article discusses the qualitative research strategies that were used to describe causal processes leading to outcomes and to identify factors that are indicative, or counter-indicative, of constructive parental involvement in children’s therapy. Using these methods it has been possible, first, to describe the dynamics of successful helping processes, second, to identify aspects of professional expertise and, finally, to identify ways in which service users are active in shaping interventions.