Full episode spoilers.
Ragnar and Horik attack Winchester, where the defenders cannot prevent the raiders from reaching its church and treasures. Athelstan's knowledge helps them identify what is worth taking, but returning to Christian surroundings also brings him face to face with his former life. He kills a young monk who surprises him and later ends the suffering of a clergyman being tortured by the other Vikings.
Ragnar hides a boy from the violence while Horik and the raiders pursue their plunder. Ecbert watches the invasion develop rather than simply throwing his full strength into an immediate response. Across the sea, Borg answers his exclusion from the expedition by attacking Kattegat. Rollo leads the available defenders, but Ragnar's best warriors are away and the town cannot hold against Borg's force. Survival requires abandoning the settlement.
Rollo helps Aslaug, her children and Siggy escape, leaving Borg in possession of Ragnar's home. Aslaug gives birth to Sigurd, whose marked eye recalls her earlier prediction. Elsewhere, Lagertha and the now grown Bjorn live with her new husband, Sigvard. His violence towards Lagertha angers Bjorn, who wants to protect her and leave their unhappy household. Lagertha tries to restrain her son even as Sigvard's treatment of her makes their position increasingly difficult.