Jupiter has been watching the battle unfolding between the Italians and the Trojans. When all the other gods are assembled, he asks them, "What's the matter? Why's this war going on? Why can't there just be peace?"
After this, Venus sees her opportunity to speak up for the Trojans. She makes a long speech, the gist of which is that the Trojans have suffered enough; if Jupiter plans to destroy them, he should just go ahead and do it, but that she should at least let Ascanius survive, even if he will live out the rest of his life ingloriously. Alternatively, Jupiter should let the Trojans go back and resettle Troy.
Now it's Juno's turn to make her own long speech. She says that what happened wasn't her fault (yeah right), and that Jupiter could have stepped it earlier if he cared so much.
Having now heard both sides, Jupiter says, "Whatever. I'm staying out of this. The Trojans and Italians can slug it out as much as they want."
Indeed, that day, the battle between the two sides continues. Nothing too important seems to happen.
That night, Aeneas sails back down the river to rejoin his companions. Since we last saw him chilling out with Evander, he has gone to see the Etruscan King Tarchon. He has brought Tarchon, along with 30 ships worth of Etruscan warriors as allies.
As they sail on through the night, Aeneas remains awake at the tiller.
Then, a bunch of nymphs swim by his ship – the same nymphs that used to be his fleet, before they were magically transformed. They let him know of the dire straits Ascanius finds himself in. Then they give him an added push to hurry him down the river.
The next morning, when the Trojans see Aeneas, their spirits revive. Turnus is excited too, because he sees an opportunity to bring the fight to the Trojans on the landing-ground.
Meanwhile, Tarchon urges his fleet to drive their ships up onto the earth. Everybody executes this maneuver successfully except for Tarchon himself; his ship splits in half on a sandbar, and many of his men are carried away by the undertow.
Scarcely any time passes before the Trojans are mixing it up with the Italians on the beach. Aeneas kills a bunch of guys. Other guys kill other guys.
At a certain point, the Arcadians, who typically fight on horseback rather than on foot, are put to flight. Pallas shouts at them, telling them they have to keep fighting – the sea is behind them; there's nowhere to run!
Then Pallas rushes into the fight and kills various guys.
The Arcadians are encouraged by Pallas's speech and behavior, and regain their courage.
In the midst of the battle, Pallas is fighting Lausus, the son of the Italian ally Mezentius.
When his sister, the nymph Juturna, tells Turnus to go help Lausus, he hops to it. When he gets to where the two young warriors are fighting, he announces that he has come to kill Pallas, and that he wishes Pallas's father Evander were there to watch. (Yikes.)
At Turnus's command, the other soldiers back away.
Pallas tells Turnus, "I'm not afraid. Bring it on."
Before throwing his spear, Pallas prays to Hercules, the god of the Arcadians, for help. Hercules hears him, but is powerless to do anything.
Jupiter tells Hercules not to worry, and that no-one can escape fate; his own son, Sarpedon, was killed at Troy, and that Turnus will die soon anyway.
Pallas throws his spear with all his strength and grazes Turnus.
Then Turnus throws his spear and gives Pallas a mortal blow. As Turnus stands over Pallas's body, he promises that his fallen enemy will be afforded all proper funerary rites. Then he takes Pallas's ornamented belt.
When Aeneas hears of Pallas's death, he gets really mad. He kills a bunch of guys around him; then he captures four guys alive so that he can sacrifice them at Pallas's funeral.
Next, when some guy named Magus falls at his knees and begs him for mercy, Aeneas refuses and stabs him in the throat.
Then Aeneas chases down some priest guy decked out in his holy robes. Aeneas kills him too.
Aeneas proceeds to kill a bunch of other guys, including a guy named Tarquitus who also begs him for mercy.
Then Aeneas takes down a guy called Lucagus who was coming at him in a chariot driven by his brother Liger. Aeneas kills Liger by spearing him in the groin. Then he drags Lucagus from the chariot and kills him as – you guessed it – he begs for mercy.
The fight keeps going on. After a little while, Ascanius and the other Trojans are able to come out of the fort – the arrival of Aeneas and his allies has taken the pressure off a bit.
Meanwhile, Jupiter is watching the battle. He tells Juno that Venus is helping the Trojans.
Juno asks to at least preserve Turnus so he can see his father, Daunus, again.
Jupiter says "Fine, I'll prevent him from dying today – just don't think I'm turning the whole war in his favor."
Juno says she's cool with that. Then, with Jupiter's permission, she heads down to earth where she makes a replica of Aeneas. She sends this replica out into the front lines of battle.
When Turnus catches sight of it, he throws his spear at it, but the replica dodges it. Then it turns tail and flees.
Thinking he's got Aeneas on the run, Turnus runs after the replica.
The replica runs onto a ship moored nearby – the ship in which King Osinius, one of Aeneas's Etruscan allies, had sailed from Clusium. There it hides.
Turnus runs on board the ship after it. Just then, Juno snaps the cable that was holding it to shore, and the boat rolls away on the surf.
Meanwhile, Aeneas – the real Aeneas – calls out for Turnus to come back and fight.
At this point, the ghostly form Turnus had been pursuing shoots up to the heavens, and the Rutulian warrior realizes he has been tricked. In his shame, he prays for his ship to come to ground on an empty coast, and debates committing suicide.
At the same time, Mezentius, the fearsome Italian ally, is making mincemeat of the Trojans.
When Mezentius gives a mortal wound to a guy called Orodes, the dying man predicts his killer's imminent death. In response, Mezentius says, "Whatever."
After the fight rages on for some time, Aeneas and Mezentius finally come together in combat. Mezentius throws his spear but it deflects off Aeneas's shield and stabs some other guy in the groin.
Then Aeneas throws his spear, which punctures Mezentius's shield and stabs him in the groin.
As Mezentius backs away slowly with this horrible wound, his son Lausus heroically runs in to the rescue. This inspires a bunch of other Italian allies to come in to Mezentius's defense, and Aeneas is held back.
Eventually, however, Lausus and Aeneas come to blows, and Aeneas stabs him through his flimsy shield.
As soon as he sees Lausus fall, however, Aeneas is moved by pity; he promises to give Lausus back to his family for burial, without taking any spoils from his body. Then he tells Lausus's fellow soldiers to come take his body.
Over by the river, Mezentius has washed his wound and is lying against a tree. When he sees his son's body brought to him on a shield, he is overcome with grief, and decides to die soon.
He gets on his horse (that must really hurt if he has a wound in his groin) and rides back to battle.
Eventually, he finds Aeneas, and they engage in single combat. Aeneas brings Mezentius down by spearing his horse in the head.
Pinned under the animal, Mezentius can't escape. He asks Aeneas to bury him in the same grave with his son.