The tale explores questions of identity, integration with society, and virtue through the adventures of Agilulf, a medieval knight who exemplifies chivalry, piety, and faithfulness but exists only as an empty suit of armour.

The protagonists of this novel are two paladins of Charlemagne: the titular non-existent knight, named Agilulf (he is in fact a lucid empty suit of armor), and an inexperienced and passionate young man, Rambaldo.

Agilulfo Emo Bertrandino dei Guildiverni e degli Altri di Corbentraz e Sura, knight of Selimpia Citeriore and Fez, is the titular character of the novel.

During Charlemagne's war against the Moors, Agilulfo is approached by Rambaldo di Rossiglione, an inexperienced and passionate young man who enlisted to avenge the death of his father, the late Marquis Gherardo, who was killed under the walls of Seville by the Argalif Isoarre.

At the end of the book, it is revealed that the entire story is narrated by Sister Teodora, a nun of the Order of Saint Columban, who was tasked with this duty by the mother superior of her convent.

While returning to camp on foot, Rambaldo discovers that this valorous knight is actually a beautiful woman named Bradamante, and he immediately falls in love with her.

Torrismondo eventually finds the Grail knights, who turn out to be a mystical sect detached from reality and devoid of ethical consciousness or tolerance for outsiders.

When Rambaldo, who has never stopped searching for her, finally arrives at her monastery, he reveals his identity; Bradamante accepts him, and they set off together into an uncertain but promising future.

[2] The Nonexistent Knight was collected together with The Cloven Viscount and The Baron in the Trees in a single volume, Our Ancestors, for which Calvino was awarded the Salento Prize in 1960.