Sometime around 1753, Monica was kidnapped by the Templars. Grand Master Reginald Birch held her hostage in his chateau near Troyes, France, and had her decode Edward Kenway's journal, which contained information on the First Civilization.
However, Monica was unable to complete her work without her son Lucio, who the Assassins guarded to keep him from being kidnapped as well. The Templars sent Edward's son, Haytham Kenway to bring Lucio in as well. Once Haytham saw how the two were treated, he had Birch promise that they would be freed after their work was finished.
In 1757, Haytham discovered that Birch had been behind the murder of his father, and attacked his chateau along with his sister and Jim Holden. After Birch had been killed, Holden freed Monica and Lucio, offering them food, horses and his own sword for their journey home. Unable to forgive Haytham for letting him suffer Birch's harsh treatment, Lucio plunged the sword into the Templar's chest. Before falling unconscious, Haytham told Holden to spare the prisoners. Holden complied, and Monica and Lucio fled afterwards.