If the Norwegian winter doesn't lay Bjorn low in season 4, a Vikings sneak attack might.

'Vikings' Season 4 Premiere: 'A Good Treason' Plot Revealed, Will Ragnar Survive?

Ragnar's (Travis Fimmel) son will head out into the wilderness to prove himself during "Kill the Queen," but the prince will have to contend with more than just nine-foot bears. When episode 3 rolls around, another threat will pop up on his radar.

"There are other forces that turn out to be plotting against him there," series creator Michael Hirst told Entertainment Weekly.

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

According to new teasers for episode 3, "Mercy," Erlendur (Edvin Endre) and Kalf (Ben Robson) will be in on a plot to harm the young warrior.

"Bjorn must fight a brutal opponent in the wilderness but will he survive the threat that Erlendur and Kalf are sending his way?" the History Channel said of the March 3 episode.

Erlendur is intent on avenging the murder of his family, and last year he teamed up with Kalf in an effort to realize his revenge. King Horik's (Donal Logue) last surviving son is ticked at Bjorn (Alexander Ludwig) for more than just Ragnar's actions. Back in Paris, Bjorn paid a little more attention to Erlendur's wife than the former prince would have liked.

Find out how the longstanding feud will play out when Vikings returns to the History Channel on Feb. 18 at 10 p.m. ET.