The use of systemic models in family therapy obliged our team to devise therapeutic tasks involving the entire family. Among these, one was found to be extremely effective: the prescribing of a family ritual. This article gives details of on such example aimed at the destruction of a myth that had been created by three generations of a family. In order that the reader may have a adequate understanding of this ritual, were shall fully describe the story of the family and of the transgenerational evolution of this myth. In the description of the treatment of the family, certain errors were made by the therapists that will come to light-errors that, as usual, were far more instructive than the actual successes. Eventually, it was the very understanding of these errors and their repercussions that led us to the successful prescription of the ritual. Finally, detailed analysis of the substance and aim of the ritual will illustrate and explain exactly what we mean by the term ritual.