Suor Teodora narrates the story of Agilulfo, a knight without a body, whose only presence is his shining armor. During the siege of Paris by Charlemagne, Agilulfo, after covering himself with glory, embarks on a quest to find Sofronia, a maiden he saved fifteen years earlier.

Accompanied by his squire, Gurdulù, Agilulfo encounters numerous adventures and is pursued by the warrior Bradamante, who is in love with him. He eventually finds Sofronia, but believing her tainted by grave sins, decides to vanish.

Agilulfo removes his armor and passes it to Rambaldo, a young comrade-in-arms. Now, it is Rambaldo who will continue the deeds of the bodiless knight, clad in the white armor.