This article presents the case of a seriously mentally ill mother and her infant who was placed in foster care at birth. The course of treatment using a mentalization-based dyadic therapy model is described with respect to the successes, challenges, and deeply painful affects that emerged along the way. The paper demonstrates the trickledown effect of the nested mentalization model, in which the therapist’s reflection of the mother’s mind allows her to be increasingly reflective of her child’s thoughts and feelings. In this case, the therapist’s goal was to help this paranoid and disturbed mother feel understood, and to help her better understand her baby. Over time and much work together, the mother developed a capacity to reflect that was not there before, and that her child has clearly benefitted from.