What happens in Canto X of Dante's Inferno?

Canto X
Curious about the shades who inhabit the burning tombs, Dante, a Florentine, wants to know if anyone he knows is suffering this gruesome eternity. Virgil replies:

They all will be closed up
When from Jehoshaphat they shall return
Here with the bodies they have left above.
Their cemetery have upon this side
With Epicurus all his followers,
Who with the body mortal make the soul;
But in the question thou dost put to me,
Within here shalt thou soon be satisfied,
And likewise in the wish thou keepest silent.”

Virgil give his charge a bit of a lesson before revealing any identities. First, he tells the younger poet that one day, the tombs will be closed. This will happen on Judgment Day. “Jehoshaphat” is a valley, and the location where God’s judgment is believed will take place. Here is Epircurus, the archest of the arch-heretics. Epicurus was a Greek philosopher who argued that the soul dies with the body. He, and all who bought into his heresy, burn forever more in Circle Six, beyond the Gates of Dis.
As Virgil is explaining, Dante hears a voice whose accent is distinctively Tuscan, the same region of Italy where Dante is from. Virgil identifies the speaker as Farinata degli Uberti. The shade has managed to struggle to a half-sitting position in order to speak to his former fellow citizen. Farinata asks Dante to identify himself by way of his bloodline. The poet readily complies but Farinata is displeased. He and Dante’s ancestors had been mortal enemies. Farinata’s family drove Dante’s people into exile:

"Fiercely adverse have they been
To me, and to my fathers, and my party;
So that two several times I scattered them."

Unabashed, Dante replies that unlike Farinata, his family lived and were therefore able to return and resume their fight. This ends the conversation between the two, because Dante’s attention is drawn to another soul who has managed to rise from the flames in order to speak. This shade is Cavalcante dei Cavalcanti, the father of Dante’s close friend, Guido dei Cavalcanti, Like Dante, Guido too went into exile when the Blacks overtook Florence.
Perhaps not surprisingly, Cavalcanti wishes to learn of the the fate of his son from the living poet. Dante has no good news for his friend’s father, but cannot seem to tell the tortured man directly that Guido is dead. Before he Dante can summon the words, Cavalcanti sinks back into his flaming sepulchre.
Farinata, who has been watching this exchange in silence, resumes his conversation with Dante, apparently caring nothing for his fellow suffering soul, Cavalcanti. He tells the poet that despite some bad blood, he alone defended Florence from the hoards who wanted to ransack the city:
Dante, however, seems less inclined to learn more about squabbling and more interested in what the future holds. He entreats the burning shade:

"solve for me that knot,
Which has entangled my conceptions here.
It seems that you can see, if I hear rightly,
Beforehand whatsoe'er time brings with it,
And in the present have another mode."

Cavalcanti discloses that while he can tell Dante the future, he, nor any of the other condemned souls, have any knowledge at all about the present:

"We see, like those who have imperfect sight,
The things," he said, "that distant are from us;
So much still shines on us the Sovereign Ruler.
When they draw near, or are, is wholly vain
Our intellect, and if none brings it to us,
Not anything know we of your human state.
Hence thou canst understand, that wholly dead
Will be our knowledge from the moment when
The portal of the future shall be closed."

Feeling a bit guilty about not telling this tortured father that his son, Guido, is indeed alive, Dante tries to make amends. He tells the shade:

"Now, then, you will tell that fallen one,
That still his son is with the living joined.
And if just now, in answering, I was dumb,
Tell him I did it because I was thinking
Already of the error you have solved me."

Dante would like to learn more but Virgil is at his elbow, pressing the poet to move on. Hurriedly, Dante inquires who else is entombed in flaming graves of Circle Six. He learns that Frederick II and the Ghibelline Cardinal are among the denziens. .
Frederick II, according to Dante, belongs here because of his skepticism towards religion. Frederick garnered so much hate for his disbelief that he became known as the “predecessor to the Anti-Christ.” The “Anti-Christ” in Christianity is the figure who appears at the end of the world; he is the “false Messiah” who leads untold numbers of people to their eternal doom.
The Ghibelline Cardinal is also punished here in Circle Six. The Ghibellines, unlike Dante’s party, the Ghelps, were contemptuous of the Church. Aristocratic and arrogant, Dante seemingly has no compunction about placing the Cardinal here.
At Virgil’s urging, the travelers move on. Dante would like to know more about the other inhabitants of the fiery tombs, but he must wait to find out. One day, Virgil explains, a woman (presumably Beatrice) will reveal all. Virgil tells his charge:

"And now attend here;" and he raised his finger.
"When thou shalt be before the radiance sweet
Of her whose beauteous eyes all things behold,
From her thou'lt know the journey of thy life."

With nothing left to say, the pair continue on. A sharp stink invades their nostrils as they descend into a valley.