In this third season, Ragnar must prove he is the right man for the position. In order to do this, he will take a very important decision and will try to fulfill his promise
Mercenary is the episode that opens the third season of Vikings. We'll see Ragnar marching toward Wessex along with Lagertha, to meet King Ecbert and demand him the promised lands. When they arrive, the King receives them and informs that the lands are available, but they must join Princess Kwenthrith's army to pacify Ecbert's men.
This will cause the distrust of Lagertha, so King Ecbert will give her the command of the viking's troops. Arriving Mercia, the battle takes place, and the foes are defeated.
This episode is a balance between the political side of the vikings, as it deepens in the personal relationships of their characters, showing different kinds of families.
Interesting fact: did you know that Travis Fimmel (Ragnar) is only 13 years older than the actor that performs his son? On the other hand, Katheryn Winnick (Lagertha) is 15 years older.