In the following paper the authors decided to discuss the „diplomatic” correspondence of the Anna Radziwiłłowa (de domo Mycielska) and the diary of the baron Charles de Saint-Pol, which are nowadays in the repertory of the Central Archives of Historical Records in Warsaw, touching the matter of the action took by the second wife of the Michał Kazimierz Radziwiłł „Rybeńko” in the case of his son „Panie Kochanku” (Karol Stanisław Radziwiłł) in the 1764.