The much awaited face-off between Ragnar Lothbrok and his treacherous brother Rollo marks the midseason finale of "Vikings" season 4. This is the ultimate showdown of the season, as it is an epic battle that will leave only one Lothbrok brother alive.

Trailer for the episode, titled "The Last Ship," reveals that Ragnar's plan to conquer Paris will be tweaked. Instead of raiding the flourishing city, Ragnar will take down his traitorous brother Rollo, who betrayed him in season 1 when he entered into an agreement with Emperor Charles.

In the episode, Ragnar's only mission will be to thrust his sword into the heart of his brother.

Synopsis for the episode reads: "A fierce battle between the Vikings and the French eventually comes down to Ragnar against Rollo and the outcome seals the fates of the two brothers."

In the teaser, Ragnar tells Rollo that one of them will die today.

"And it won't be me," says Rollo.

While Ragnar has been relatively weak after being seriously wounded during a raid in Paris, his eagerness to take down Rollo will give him enough strength to withstand the biggest battle of his life yet.

Meanwhile, Rollo will also brace himself for the epic battle so as to prove to everyone that Ragnar is no better than him.

Aside from the battle between Ragnar and Rollo, the midseason finale will also follow Ragnar's ex-wife Lagertha, whose life will be put in jeopardy by a French warrior.

The next episode of "Vikings" season 4 airs on April 21 on History Channel.