Full spoilers for this episode.
Ragnar's new expedition reaches Northumbria and attacks the English camp at night. His men capture Aelle's brother, giving him a prisoner important enough to bring the king to negotiations. Aelle's advisers disagree over whether the raiders are a religious threat or men who can be paid to leave. Ragnar accepts an invitation to the royal villa, where a feast brings the visitors and their hosts into uncomfortable contact before they discuss terms.
Ragnar demands two thousand pounds in gold and silver for the prisoner's release and his departure. Aelle agrees, requiring the raiders to stop attacking while payment is collected and one of them to accept Christian baptism. Rollo volunteers and treats the ceremony as a practical joke, but Floki condemns him for insulting their gods. The promised treasure arrives in empty chests, followed by an English ambush that the raiders fight off with losses.
Ragnar kills Aelle's brother after the betrayal and sends his body back, prompting the king to swear revenge. In Kattegat, Lagertha governs during her husband's absence and protects a woman accused of adultery. She also welcomes Siggy into her household and extends protection to Thyri. Her own pregnancy ends in miscarriage, with Siggy helping her through the loss. Ragnar's victory in England happens far from the family grief Lagertha faces while he is away.