This article aims to understand the path that leads a mother to kill her child and the reasons of such an act during which the death drive annihilates the life drive. More specifically, we examine the function of the act of filicide for mothers for whom the experience of the construction of the primary bond turned out to be harmful and lead to a suffering impossible to depict, causing a failure for the subject in her abilities to become a subjective individual and to take on an identity. Basing ourselves on a clinical case, we examine the psychic function of the act of filicide with regard to one’s individual story. In order to do this, we study the developments of feminine subjectivation in its relations to the female/maternal and to the male/paternal. Finally, we discuss the transference and counter-transference stakes in the encounter and the therapeutic work with a mother who was the perpetrator of the murder of her child.