At the end of the third day of storytelling in the Decameron the reigning king, Filostrato, proposes the theme of love stories with unhappy endings to the group. His directive is met with resistance, as is particularly apparent in the response of Fiammetta who laments: "Cruel indeed is the topic for discussion assigned to us today by our king, especially when you consider that, having come here to fortify our spirits, we are obliged to recount people's woes". Despite her resistance to the theme as expressed in the narrative frame, Fiammetta adheres to it as she recounts the day's first story. Her tale of a princess' forbidden love for a commoner and of a king's excessive paternal affection for his daughter ends bitterly for all. Embittered by his own frustrated expectations of love, the king is neither able to accept nor to appreciate the happiness the lovers have found in each other. He responds by attempting to make them suffer but in the end succeeds only in bringing a greater suffering upon himself. Fiammetta's king could very well represent the king of the day, Filostrato, whose name means "frustrated in love" and whose imposition of a "tragic" theme is intended, perhaps, to make his companions feel as despondent as does he. In this way, though following the day's theme, Fiammetta's story contains a certain subversive quality, a subtle blurring of the roles between lover, beloved, and father that puts the focus of the tragedy not as much on the moribund lovers as on the party most vexed by their love - the king. The moral message for Filostrato, therefore, is that by forcing his will upon others he is likely to cause further injury to himself. Fiammetta, while appearing to defer to Filostrato's authority, is in effect offering a poignant critique of his judgment.
The relationship between Tancredi, Ghismonda, and Guiscardo seems to mirror a courtly love triangle, with Tancredi in the role of the betrayed lover. Tancredi is motivated by jealousy and a desire to punish his beloved Ghismonda when he condemns Guiscardo to death and then, in a particularly cruel gesture, has his excised heart presented to Ghismonda in a golden chalice.
In medieval popular belief, the heart was the physical seat of love in the body. By presenting Ghismonda with the lifeless heart, Tancredi intended to end the affair by extracting Ghismonda's love from the very core of his being. Ghismonda responds by appropriating her father's symbol of triumph. Looking upon Guiscardo's heart in the chalice she exclaims, "Nothing less splendid than a golden sepulcher would have suited so noble a heart; in this respect, my father has acted wisely." Upon seeing the heart, Ghismonda manages to draw strength from it. By crying over it, kissing it, and caressing it, she honors Guiscardo's memory and pays homage to the love they shared. Like an amulet, it protects her from further heartache by becoming the means of her suicide. She creates a special potion - a pharmakon in the double sense of "cure" and "poison" - which she mixes with her tears, pours over the heart, and drinks. Before dying she places Guiscardo's heart upon her own, symbolically representing their love's victory over Death.
Ghismonda and Guiscardo are dead, and yet Tancredi ultimately emerges as the most tragic character. In the final analysis it is truly he who suffers the greatest loss - the loss of love, honor, and respect as well as the loss of his beloved daughter and his capable servant. In the end, "after shedding countless tears and making tardy repentance for his cruelty, he saw that (Ghismonda and Guiscardo) were interred together in a single grave, amid the general mourning of all the people of Salerno." Ghismonda and Guiscardo are forever honored for the deep and noble nature of their love, whereas Tancredi reaps only grief and remorse for the misbegotten expression of his. The parallels between the King Tancredi and the brigata's king are apparent to all, including Filostrato himself who waits his turn (IV.9) to voice a response to Fiammetta in a story of his own.