Dante lingers looking for a kinsman among the mutilated of the ninth bolgia — Geri del Bello, his father's cousin, murdered and unavenged. Virgil tells him he glimpsed Geri shaking his fist at Dante as they passed. Dante is moved: the blood-debt is unresolved and Geri knows it. Virgil gently urges him on. The tenth and final bolgia of Malebolge: the falsifiers, divided into four categories across Cantos XXIX and XXX. Here first are the alchemists — falsifiers of metals — who lie heaped across each other in the ditch, scratching themselves raw with their nails, unable to stop. Leprosy, scabs, mange: the itching is permanent, the relief never comes.
Griffolino d'Arezzo laughs as he tells his story: he once told the Bishop of Siena's son that he could teach the boy to fly; when the boy found he couldn't, he told his father, who had Griffolino burned as a sorcerer. The real alchemy he practiced for profit Griffolino doesn't mention — his companion Capocchio fills it in: he was a genuine alchemist who could imitate metals perfectly. He and Dante knew each other in Florence; Capocchio reminds him of this, calling Dante a fine observer of nature — his transmutations in poetry were, after all, a kind of alchemy too.