Dante wakes up to find himself at the edge of a great dark valley, in which he cannot see anything. (Yes, they crossed the Acheron while Dante was unconscious.)
Virgil says "Let’s go." But he’s really pale.
Dante mistakes Virgil's paleness for fear and balks. But Virgil explains that his alabaster complexion does not indicate fear, but rather sympathy for his neighbors. Because this is his home in Hell—Limbo.
Here, the sinners sigh as well, but not nearly as loudly or painfully as the neutrals.
The inhabitants of this circle of Hell are those who had no control over their salvation: they were either not baptized at birth or born before the coming of Christ. Thus, they don’t suffer as much as other sinners; they only feel the absence of God’s love as a constant ache. Otherwise, they frolic in their pretty fields.
(We know what you’re thinking: this is Hell? But trust us, it gets much worse.)
Saddened by these sinners’ plight, Dante earnestly asks Virgil whether or not anyone is allowed to leave this place (and presumably enter Heaven) if they are good people.
Kindly Virgil answers yes; in fact, he saw it happen. With his own eyes, he saw Christ enter Limbo and take Old Testament worthies like Noah, Moses, Abraham, David, and Rachel into his all-forgiving arms and transport them up to Heaven. (Trivial Pursuit tidbit: this was called the Harrowing of Hell.)
Suddenly, Dante sees a fire break up the darkness. The fire is the glow of a luminous castle and men are there.
To answer Dante’s inevitable question, Virgil introduces the men as his best buddies, fellow poets like Homer, Horace, Ovid, and Lucan.
Virgil chats with his friends for a little while before they notice Dante and invite him in. Dante is ecstatic at being "sixth among such intellects."
This circle enters the shining palace and its countless flowering courtyards and gardens. Inside, they encounter a bunch of Greek and Roman heroes like Hector, Aeneas, Caesar, Socrates, Plato, and many more.
When they’ve had their fill of reciting poems, Dante and Virgil take their leave.
Every step forward brings them into darker and darker territory.