Commander Louise Chaland, supported by her son Sylvain, a priest, investigates the murder of a subversive sculptor whose body was found next to one of his canvases covered with Latin inscriptions. They quickly made the link with the disappearance of a relic of Saint Martin, patron saint of Tours. Their investigations led them to a refuge for the needy, run by François Delcourt and his daughter Agnès, who had romantic ties with the sculptor found murdered. How can we not be disturbed by the importance that some attach to this relic? This investigation will lead them to discover the historical and religious heritage of the city and to a kind of "reconciliation" between the lay mother and the son who has become a priest.