Ragnar Lothbrok and his brother Rollo return from a battle in which Ragnar has visions of the god Odin and his valkyries. Home again, Ragnar takes his son Bjorn to Kattegat so that Bjorn may undergo his rite of passage. Left at home, Ragnar's wife Lagertha quickly dispatches two would-be rapists. In Kattegat, Ragnar convinces Rollo that raids to the west are worthwhile and possible thanks to new navigational tools but is rebuked by his ruler, Earl Haraldson, who orders raids into the Baltic as usual and has the upstart Ragnar watched. Bjorn and Ragnar visit Floki, a gifted shipwright and Ragnar's friend. He has been secretly building a new type of longship, which they successfully test. Meanwhile, back at home, Rollo makes unwelcome advances on Lagertha.
Vikings follows the adventures of Ragnar Lothbrok the greatest hero of his age. The series tells the sagas of Ragnar's band of Viking brothers and his family, as he rises to become King of the Viking tribes.
As well as being a fearless warrior, Ragnar embodies the Norse traditions of devotion to the gods, legend has it that he was a direct descendant of Odin, the god of war and warriors.