"The Profit and the Loss" is the seventh episode of the fourth season of Vikings. It is the thirty-sixth episode of the series overall. It first aired on March 31, 2016. It was written by creator Michael Hirst and directed by Ken Girotti.
In England, King Ecbert schemes to secure the crown of Mercia, while outside Paris, a considerable force of Vikings attack Rollo's defenses. Also, the mysterious wanderer Harbard returns to Kattegat and causes a stir among the women.
Ragnar suggests attacks from the river and the land. From towers on the opposite sides of the river, crossbowmen fire down on the advancing Viking fleet. High above, Rollo notices Lagertha's land attack from the rear as her warriors become stuck in a marsh. Crossbowmen advance from the towers to assault Lagertha's warriors.
As the Viking ships approach the forts, Rollo orders the Franks to raise a large metal chain between the forts, which capsizes Harald's ship.
Lagertha's ground attack retreats, taking heavy fire from crossbows. The Franks begin to light the Viking ships on fire through bombs of oil and flaming arrows. Harald and Halfdan are rescued by Bjorn, and Ragnar saves Floki from drowning. As the Viking ships retreat, Ragnar angrily yells to Rollo that he saved his life when everyone wanted him dead.
In Kattegat, Sigurd watches from a distance as Harbard and Aslaug kiss. In Wessex, Ecbert leaves for Mercia. He arrives to meet with Prince Wicksten of Mercia. He tells Ecbert that he will hand over Mercia to him.
In Paris, the Vikings arrive back at camp, which the Franks have ambushed. Helga is alive but severely wounded, while Ragnar's sons and Yidu are unharmed. Ragnar demands more "medicine" from Yidu.
Floki has a vision of Harbard having sex with Aslaug. Bjorn demands a plan of attack from Ragnar. Ragnar responds they will retreat tomorrow, while mumbling to a severed head.
- Travis Fimmel as King Ragnar
- Katheryn Winnick as Lagertha/Earl Ingstad
- Clive Standen as Duke Rollo
- Gustaf Skarsgård as Floki
- Alexander Ludwig as Bjorn
- Alyssa Sutherland as Queen Aslaug
- Peter Franzén as King Harald "Finehair"
- Jasper Pääkkönen as Halfdan "The Black"
- Kevin Durand as Harbard
- Linus Roache as King Ecbert
- Dianne Doan as Yidu
- Maude Hirst as Helga
- Owen Roe as Count Odo
- Edvin Endre as Erlendur
- Georgia Hirst as Torvi
- Morgane Polanski as Princess Gisla
Additional Cast (in order of appearance)
- Stephen Rockett as Hvitserk
- Luke Shanahan as Ubbe
- Huw Parmenter as Roland
- Elijah O'Sullivan as Sigurd
- Philip O'Sullivan as Bishop Edmund
- Des Carney as Waerferth the Scout
- Ceire O'Donoghue as Third Young Woman
- Declan Conlon as Wigstan