Ivar slithers towards his flagship, a demon ready to haunt his enemies.
Now I can finally fulfill my promise to the gods and kill Lagertha!
he tells his brother Hvitserk.

Credit: Jonathan Hession/Histroy Channel
Theyve come far, these sons of Ragnar.
They have avenged their father and will they now kill their brothers?
Would you kill Ubbe?
Ivar asks his brother.
If I kill Ubbe, wont my fame be assured?
says Hvitserk, answering with a question.
All prepare for battle.
In Kattegat, Margrethe remains behind while so many others go.
You may recall that Guthrum was the biological son of Jarl Borg, long-ago enemy of Bjorns father Ragnar.
But Guthrum never met that man, seems to regard Bjorn as something like a father.
Of course, family members can hurt each other just as much as enemies can.
On the field of battle, Lagertha begins to wonder.
Is there another way?
It is not right that the sons of Ragnar should try and slaughter each other, she says.
Both sides seek to turn their hostages into allies.
Brothers reach out to brothers: Ubbe and Hvitserk, Harald and Halfdan.
Perhaps diplomacy will win the day.
A great summit is held, flags all around.
Bjorn Ironsides begs the assembled to consider the possibility of peace.
A civil war can only bring tragedy, and a lifetime of revenge obligations for those who survive.
You imagine theyll fight this battle the rest of their lives.
He wants to win the whole world.
Lagertha speaks to his chief ally, Ivar.
Win or lose, you lose, she says.
Ivar sheds a tear.
He says that he will renounce his promise to kill Lagertha.
He says they are all sons of Ragnar.
I might break a bone, he says, but I can never break a promise.
So a great peace is averted, and so there must be a battle.
The Vikings have turned their energies inward, battling amongst themselves.
Further afield, distant lands offer new possibilities.
Alfred has returned to Wessex and sees his own society ossifying.
And in the distant land of the gods, Flokis followers continue building a new society.
Pride and jealousy threaten this new land.
Floki himself declares that they must build a temple honoring Thor.
But will they have food for the winter?
And what if they cannot grow a crop here?
Floki sits back, pondering, silent.
Floki and Alfred dream of a new world.
The Northmen are fighting to control the old one.
Minutes from battle, Ivar conceives a strategy.
They should pull back a third of the army to protect their ships.
And Hvitserk should carry some warriors through the forest, to flank their enemies.
It is a disaster.
Lagertha has allies waiting in the forest for Hvitserks men.
Shieldmaidens flank Haralds own forces, demolishing them.
A horn blows for reinforcements, but far from the battle, Ivar believes they are too late.
There are great losses in the battle, arms torn asunder, skulls hammered.
Bishop Heahmund is cut down, left bleeding on the ground.
He is discovered, in the victorious aftermath, by Lagertha, who declares that he must be saved.
Maybe the gods know why, she says.
Maybe she just wants to take the warrior priest as a souvenir.
Harald flees, staring daggers towards Ivar.
Lagertha and her allies have won the battle.
But a battle is never the whole war.