'Vikings' season 4 episode 13 spoilers: Ragnar's fleet gets shipwrecked; Rollo considers joining Bjorn's voyage

Ragnar (Travis Fimmel) makes a tough decision in the upcoming episode of History's hit drama "Vikings" season 4.

Titled "Two Journeys," next week's episode will see Ragnar fail to complete his voyage. According to the official synopsis for episode 13, Ragnar's fleet is shipwrecked and eventually washes up on the coast of Wessex. Since there are not enough survivors to organize a credible force, Ragnar and his son, Ivar (Alex Høgh Andersen), are forced to make a difficult decision and change their plans.

After meeting his Viking comrades once again, Rollo (Clive Standen) can't resist the urge to join Bjorn's (Alexander Ludwig) voyage. However, his decision to join them may cost him his new Frankish identity and his marriage. Ragnar is also facing a similar complication as he must take a risk and carry Ivar towards the Royal Villa located in Wessex — throwing himself and Ivar upon King Ecbert's (Linus Roache) mercy.

Based on the history books, Ivar the Boneless was a Viking commander that ended up leading the Great Heathen Army who was behind the invasion of England during the late 800s. The previous episode of "Vikings" showed Ragnar asking Ivar to go to England with him, despite his physical limitations as a cripple.

In a recent interview with Variety, executive producer Michael Hirst teased that Ragnar's reason for bringing Ivar in his voyage will soon be explored in the plot as he continues to drag his son around England.

"Ragnar says, 'I know that, of all my sons, you will be best placed to revenge me, and everyone else will reject you. You are full of anger, but you can use that anger, and you can become extraordinarily special.' Having tried to kill him off as a baby, Ragnar recognizes something in Ivar that is valuable and good. Ivar will become, historically, the most famous Viking. In this season we'll get to that," the EP explains.

The fourth season of "Vikings" airs every Wednesday night at 9 p.m. ET on History.