Spoilers for this episode.
The Vikings attack Paris from land and water using the equipment Floki has built. Lagertha's force advances against the gates while the river assault brings siege towers to the walls. Count Odo's defenders answer with crossbow bolts, stones, fire and hot oil. Gisla appears above the fighting to rally the city's soldiers, and the attacking warriors discover that reaching a wall or doorway does not mean they can hold it.
Ragnar and Bjorn fight on the ramparts, but the assault becomes a retreat. Bjorn is hit by arrows and brought back badly wounded, while Ragnar suffers a heavy fall. Floki watches his siege machines burn and becomes trapped amid the wreckage, his confidence in divine support collapsing with the attack. Kalf pulls Lagertha out of danger at the gate despite her resistance, saving a woman who still regards him as the thief of her earldom.
Back in camp, Lagertha fears for Bjorn and challenges Ragnar over the danger their son faced. Ragnar insists that Bjorn must be allowed to act as a man. His own injuries are also severe, and he turns toward the memory of Athelstan while keeping his distance from Floki. Lagertha sleeps with Kalf but tells him she still intends to kill him. Paris remains beyond the attackers' control, and survival has brought no settlement to the arguments inside their camp.