The article wants to examine the particularity of infanticide, starting from the follow-up in prison of a mother who killed her child. We will consider how the dynamics of the link resonate with traces of ancient experiences that remain under the influence of the primary object. Generally the act represents a moment of extreme distress that can neither name itself nor think nor integrate itself into a life that seemed well regulated. These patients come from a social and cultural background that is often favoured. They have never had a previous criminal conviction.The article retraces the different stages of the clinical encounter, with the conduct of two projective tests (the Rorschach and the TAT) which show signs of rupture, break of subjectivity, that is, a defect in the transformation of the tried and tested who break again into the primary relationship with the child. The clinical follow-up of this mother, based on the projective material, shows that the investment of the child is part of a self-repair. If the bond merges with the child remains very idealized, it covers the fear of a painful disillusionment and without warning. As soon as this unit is compromised, the subject is prey to a traumatic reviviscence that awakens the feeling of an immeasurable libidinal infirmity. This trauma is anticipated and actualized in the act by the murder of the libidinal object, by the murder of the child.