Some mothers who have recently lost a significant attachment figure may become mentally incoherent and sporadically even enter a trancelike, dissociative state. Such states of mind have been shown to predict infant attachment disorganization. Infants born close to the time of a parental loss are at a greater risk for intergenerational trauma. A background of maternal substance abuse is also known to increase such risk. We illustrate by way of a case study how a mother–infant group psychotherapy programme aimed at substance-abusing mothers may help to prevent the transmission of mother’s unresolved trauma to the infant. Another goal was to discuss how attachment-derived methods (namely, Adult Attachment Interview, Strange Situation Procedure and the Emotional Availability Scales) may aid in understanding the effects of the intervention.