Close observation of the interactions between a traumatised mother and her infant son provides information on the modes of transmission of psychic trauma in the mother-infant dyad. Following the presentation of a current literature review on the theme, the subject of "radioactive residue" and counter-transference in the transmission of psychic trauma from mother to infant will be illustrated through a clinical case study that focuses on a Haitian mother and her two-year-old infant son who has been referred to a "transitional care nursery" in urban Paris. The encounter with this mother-infant dyad is analysed through observing the quality of the interactions that take place between the mother and infant in order to determine how a particularly traumatic narrative impacts the mother-infant relationship, in addition to relations with the clinician. Mother and infant respond to one another through the "emission" and reception of "radioactive residues" as hypothesized by Gampel. This clinical case study shows that there is a need to consider transcultural factors and collective experience and history when analysing traumatic events. Additionally, the case study shows that counter-transference can be an effective clinical tool for gaining access to an infant's experience as the recipient of a traumatic narrative.