Charles de Louviers, seigneur de Maurevert, is not only the assassin known for his attempt on Coligny’s life on 22 August 1572, for he was also a provincial nobleman. This article, which is based on a study of the notarial acts passed at Chaume-en-Brie, close to his castle, seeks to shed light on his life choices and on his entourage, specifically for the year 1572. Maurevert had several important acts passed in June 1572, showing that he was anticipating his departure from his castle two months before the failed assassination (letting of several properties, acquisition of others). These efforts suggest that the plot had been in preparation well ahead of the famous 22 August 1572 date, and that it was not a botched last-minute job. Moreover, Maurevert’s entourage was well-integrated at the court: his wife’s first cousin, Anna d’Acquaviva, was the mistress of Charles IX in March 1572; and his neighbour, Jean de Condi, abbot of Chaumes, was the brother of the count of Retz, chief of Catherine de Medici’s secret agents. Finally, one of Maurevert’s friends, Jean Hanoyer, climbed high up the social ladder, becoming provost of Chaume in December 1572. Taken together, the details unearthed show that the assassination attempt of 22 August had been carefully prepared by Maurevert beginning in June 1572, and that he benefited from the support of royal power for the promotion of a friend soon after the St. Bartholomew’s Day Massacre.