Marital bliss will be a foreign concept for the Lothbrok brothers when Vikings returns for season 4.

'Vikings' Season 4: Ragnar's Fate Revealed In Premiere PHOTOS, Problems For Bjorn

In Kattegat, Ragnar's (Travis Fimmel) philandering ways and Aslaug's (Alyssa Sutherland) lust for power will have the King and Queen on edge. In Paris, Rollo's (Clive Standen) murderous past will turn his new wife into his staunchest adversary.

The first preview for the season 4 premiere, "A Good Treason," shows the latter's conflict as the pair attempts to take to their marital bed. Princess Gisla (Morgane Polanski) pulls a knife on her new hubby, and Rollo's reaction to the entire affair is rather surprising.

'Vikings' Season 4: First Look At Bjorn's Most Dangerous Foe, New PHOTOS

"We're going to see a completely different Rollo, if he's ever going to conquer Paris and conquer the princess," Standen teased, according to Entertainment Weekly. "He has to be far more cerebral, he has to be on his A-game all the time, and his attitude to Ragnar has to change."

Find out how he will do so when Vikings returns with a 20-episode fourth season, "A Good Treason" will kick off the run on Feb. 18, and the premiere will be followed by "Kill the Queen," "Mercy," and "Yol."

Vikings airs Thursdays at 10 p.m. ET on The History Channel.

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