'Vikings' season 4 episode 17 recap: Ragnar's sons plan to avenge his death

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"Vikings" season 4 episode 17 is titled "The Great Army," and although there really is no army yet, the episode showed what the brothers are planning to do to avenge their father.

The most recent episode started with Lagertha (Katheryn Winnick) watching over the construction of the wall that is being built to protect the village.

It wasn't long until the scene shifts to a small altercation among the brothers, and it seems that despite their common goal of avenging their father, Sigurd Snake-in-the-Eye (David Lindström), Ivar the Boneless (Alex Høgh), and Ubbe (Jordan Smith), three of the four sons of Ragnar Lothbrok (Travis Fimmel) and Aslaug (Alyssa Sutherland), cannot get along.

When things settled down among the brothers, they were able to agree that they not only need to target King Aelle (Ivan Kaye), but they should also go after King Ecbert (Linus Roache) as he was the one who decided to sacrifice Ragnar.

It wasn't long before the brothers agree that they would need to make a sizable army — one that is double the size of what their father was able to gather.

The episode also showed Bjorn Ironside's (Alexander Ludwig) fortunate return to Kattegatt, which is one of the main reasons Lagertha is still alive despite Aslaug's sons' desire to kill her.

Although Aslaug's sons want to avenge their mother, the brothers are still hesitant in killing Lagertha since they need someone to rule Kattegat while they sail off to deliver their father's revenge. Also, they know that killing Lagertha would mean that they would also have to kill Bjorn, which is something the brothers are not keen on doing. Still, it seems like Ivar is planning something on his own.

On the other side of the world, King Ecbert is teaching Alfred (Conor O'Hanlon) a number of great lessons in ruling a kingdom, and the king seems to be grooming him for the job. The king informed him that he should have his own thoughts and that he should not let himself be influenced.

The next episode of "Vikings" season 4 is titled "Revenge," and it will premiere on Wednesday, Jan. 18, at 9 p.m. EST on History.