"Vikings" is gearing up for its return to the History Channel as the series continues to draw in viewers with its unique storyline that's rooted in actual Viking history. This season, the focus will be on Ragnar (Travis Fimmel) and Rollo's (Clive Standen) already fragile relationship as the brothers continue to be at odds with each other, while Lagertha (Katheryn Winnick) is caught in power struggles with Kalf (Ben Robson).

According to the official synopsis for season 4 of "Vikings," season 3 ended with the extraordinary battle in Paris, where Ragnar was able to gain victory which came with a cost, as he returned to Kattegat dangerously ill. Thoughts of his death spur Queen Aslaug (Alyssa Sutherland) and his oldest son Bjorn (Alexander Ludwig) to succeed Ragnar as king.

Meanwhile, Lagertha continues power struggles with her conniving former second in command, Kalf. Rollo betrays his Viking heritage by staying in Frankia, and Floki (Gustaf Skarsgard) is captured for his torture and murder of the Christian priest Athelstan.

In the new promo for the series, the Vikings are seen back at sea, and later, Queen Aslaug is heard asking if a woman will succeed to the kingdom of Kattagat. Lagertha is seen standing with a group of women while wearing a gown spattered with blood.

The battle continues and the King of France is seen talking to Rollo, telling him that the Vikings are back at sea and that they fly the banner of Ragnar.

"For the sake of Paris, do not return to your brother," the king implores Rollo.

Rollo continues to pursue his ambition as he vows that he will stop at nothing to get whatever he wants.

"I will sup with the devil if he will show me how to achieve my earthly goals," he says.

But Ragnar will be putting a stop to it as he gives his word that things will be decided when Rollo returns to Kattagat.

"When my brother returns, everything will be decided here," Ragnar says.

"Vikings" season 4 premieres on Feb. 18 at 10/9c on History.