In the year 1467 the hostilities between the Duchies of Milan and Savoia had forced Galeazzo Maria Sforza, Duke of Milan to move out along the River Sesia. This marked the boundaries between the two States and it was here that he had decided to take a stand against the troops of Amadeo IX of Savoia. The Duke sent a young Captain, Messer Matteo de Grandis, to coordinate the troop movements in the area around the Lake.
Messer Matteo was billeted during his mission in the fortress at Oleggio Castello, which belonged to Lord Alberto Visconti, a distant cousin of the Duke's mother, Bianca Maria On his arrival, Messer Matteo was received with great ceremony by Lord Alberto, his wife Beatrice and his daughter Barbara. Matteo immediately fell under the spell of the beautiful young girl, a singular mixture of beauty and virtuosity, combined with a generous heart.  However, her hand had already been promised in marriage to a neighbour’s son, in order to cement an important political alliance.
In the days that followed messer Matteo was able to meet madonna Barbara several times. His thoughts, even when busy preparing for war, were always about her. Madonna Barbara was also attracted to the young captain Matteo, for although he was a fighting man, he had shown that he possessed an out of the ordinary degree of sensibility.
There was no lack of opportunity for Barbara and Matteo to be together both in the Castle Rooms and walking through the Castle grounds down to the Lake.  Thus burgeoning love enveloped the young pair, binding their souls for all eternity.  As the day of messer Matteo's departure drew closer, the two lovers decided to seal this tender sentiment before God.
They met in the Chapel, and oblivious of the world around them, of their duty and of their families, they swore eternal fidelity, sealing their love before God with a kiss. Although they wished that these idyllic days could last for ever, the troops were ready to leave for Ghemme, where Duke Galeazzo Maria had pitched his camp. Thus Matteo had to leave the Castle and his beloved Barbara. The promises of love exchanged turned out to be meaningless.
The day after the Captain's departure madonna Barbara, unable to resist being separated from messer Matteo, tried to leave the Castle to be with her lover. However, her father, suspecting something was afoot, had had her watched by his retainers, and stopped her from fleeing. During the ensuing scuffle, madonna Barbara confessed to her father, Lord Alberto, her undying love for messer Matteo. He reminded her that she had already been promised in marriage to someone else, and in the face of her refusal to obey him, he commanded her to forget messer Matteo and had her locked in the Castle Tower.
Lord Alberto immediately wrote to the Duke, complaining as to how messer Matteo had taken advantage of his hospitality and had seduced his daughter, who was already promised to another man and demanding retribution. 
Galeazzo Maria Sforza, was justifiably annoyed by Visconti's letter and on the advice of his secretary Cicco Simonetta, decided to send messer Matteo to escort his brother Tristano and the painter Zanetto Bugatto to the Court of France, where they were to make the acquaintance of Bona di  Savoia, his future bride.
Matteo was ordered to remain in France at the court of Louis XI , until specifically recalled.
Madonna Barbara, not informed of messer Matteo's enforced departure, waited in vain for her lover's return. The days turned into weeks and then months, and the young damsel, refusing to come out of her room and eat, slowly wasted away.
Deprived of Matteo, she was unable to find any kind of solace, refusing to see even her mother. Doctors and family were impotent in the face of her unremitting love for the absent young captain of the guard and she finally died of despair, her heart broken. Sometimes, during the night , it is possible to hear sighs and laments coming from the Tower.
Some say that they have seen a shadow looking out from the window, as though someone was watching the Lake: popular belief maintains that it is the ghost of the beautiful Barbara, which stills wanders restlessly around the Castle Tower searching for her lost love.