Dante comes to and finds himself in the third circle of hell, where rain never stops falling, mixed with sleet, snow, and hail. The horrid three-headed dog Cerberus continually mauls and bites the souls in this part of hell. The souls cry out and try to avoid the terrifying creature, but in vain.
Dante takes Cerberus from the underworld of Greek mythology, though here the creature is enlisted to help deliver the punishment ordained by God for sinners.
When Cerberus sees Dante and Virgil coming, Virgil scoops up several handfuls of dirt and throws some in each of the creature's mouths. This subdues Cerberus, allowing Dante and Virgil to pass by the suffering souls lying on the ground. One soul sits up and speaks to them, claiming that Dante knows him. Dante does not recognize the soul, who identifies himself as Ciacco, a citizen of Florence (where Dante is from). Ciacco says that he suffered from the sin of gluttony, as did all those in this circle of hell. Dante pities Ciacco and asks if he knows what will become of their city, Florence.
Ciacco is eager for the opportunity to speak with a living soul like Dante. While Dante is exploring the afterlife and journeying toward God, he is still troubled by earthly concerns, as his interest in Florence demonstrates. And many of the dead souls in hell have similar earthly concerns, wanting to know about goings in in the world regarding people and cities.
Ciacco foretells violence and turmoil for Florence between its different political factions, spurred on by Avarice, Envy, and Pride. Dante further asks Ciacco about various famous men of Florence who have died and Ciacco tells him that they are deeper in hell. Dante will see them when he ventures further below. Before falling back to the ground, Ciacco asks Dante to remember his name when he returns to earth.
From his position in hell, Ciacco is able to foresee events on earth. The favor he asks of Dante is an example of how earthly fame is the only (small) consolation souls in hell can hope for. By including Ciacco's name in his poem, Dante carries out Ciacco's request.
Virgil tells Dante that when the final judgment comes, these souls will be reunited with their earthly bodies. Dante asks if their pain will then be greater or lesser and Virgil explains that, since Judgment Day leads to the perfection of all things, their suffering, too, will be perfected. That is to say, their pains will be even worse. Virgil and Dante descend to the next circle of hell.
Here Virgil gives some further explanation of God's system of justice. God's judgment leads to the perfection of all things: for sinners, this means the corresponding and appropriate punishment and suffering that their sins require.