Betray Ragnar (Travis Fimmel) once, shame on you. Betray the King of Norway twice, well … now you're just asking to have your head cut off. And a murder plot is exactly what wll run through the great Ragnar Lothbrok’s head when he learns his treacherous brother, Rollo (Clive Standen), has sided with the Franks over his own people.

According to midseason promo video for History Channel’s “Vikings,” Ragnar will come face-to-face with his disloyal brother in an upcoming Season 4 episode of the epic drama.

“When everyone wanted you dead, I kept you alive,” Ragnar reminds his brother that the only reason he’s alive is because he bribed a judge to spare his brother’s life. (Rollo had betrayed his brother in Season 1 after teaming up with Ragnar's enemy, Jarl Borg [Thorbjørn Harr].)

But Rollo isn’t phased by the comment. He has long wanted to inch out of the shadow of his famous sibling — and he’s closer than every before of becoming more than just Ragnar’s brother.

After getting married to Emperor Charles’ (Lothaire Bluteau) daughter, Princess Gisla (Morgane Polanski), Rollo is now a powerful — and extremely wealthy — Count. But as long as his brother is still breathing, Rollo can never fully be the warrior he was fated to be. He also tells the people of Paris that they will never be truly safe until Ragnar is dead.

“As long as my brother is still alive, he is not defeated,” Rollo says.

And, apparently, Ragnar feels the same way, which is why he proposes a duel between the brothers in the drama-drenched promo video.

“One of us will die today,” he warns Rollo.

“And it won’t be me,” Rollo barks back.

“Vikings” airs Thursdays at 10 p.m. EDT on the History Channel.