What happens in Canto VIII of Dante's Inferno?

Canto VIII
Phlegyas paddles his charges across the Styx and away from the them pitiful souls mired in the slime. Dante and Virgil now can see the City of Dis more clearly; the rounded tops of the city’s mosques glow red. Virgil explains that

"The fire eternal
That kindles them within makes them look red,
As thou beholdest in this nether Hell."

Coming closer still, Dante can see that the fire-lit mosques are protected by a deep moat and walls of what appear to be iron. Phlegyas takes a circuitous route but finally announces they have arrived, “Debark,” he orders, “here is the entrance."
Rather forced to oblige, Dante steps onto the shore. He is stunned to see vast numbers of guards at the gates. These protectors angrily demand

“Who is this that without death
Goes through the kingdom of the people dead?"

Virgil moves to calm the angry hoard but his words are of no comfort to Dante. The throng will let Virgil, a shade, pass through but the deny the living Dante entrance:

"Come thou alone, and he begone
Who has so boldly entered these dominions.
Let him return alone by his mad road;
Try, if he can; for thou shalt here remain,
Who hast escorted him through such dark regions."

Dante begs the great poet not to leave him, reminding Virgil how exclusively he has relied on the older man’s guidance. If we must go back, please come with me, Dante implores:

"O my dear Guide, who more than seven times
Hast rendered me security, and drawn me
From imminent peril that before me stood,
Do not desert me," said I, "thus undone;
And if the going farther be denied us,
Let us retrace our steps together swiftly."

Virgil tells Dante to not be afraid and that he will take care of things. Unfortunately, and to his likely surprise, Virgil fails to gain Dante passage. The poet returns to his charge downcast but still determined. Virgil recalls that this same throng once tried, and failed, to block Christ’s entrance. They too will eventually be victorious:

"Fear not, for I will conquer in the trial,
Whatever for defence within be planned.
This arrogance of theirs is nothing new;
For once they used it at less secret gate,
Which finds itself without a fastening still.
O'er it didst thou behold the dead inscription;
And now this side of it descends the steep,
Passing across the circles without escort,
One by whose means the city shall be opened."

This brief delay may be a reminder to Virgil that no one, not even someone as great as himself, is more important than Christ or receive better treatment than the Savior.