When arriving in Lunden, they find the city empty. In the television series, in " Episode 2.6", Lord Æthelred is put in charge of the men. Lunden's recapturing King Alfred sends out men to recapture Lunden.The probable reason for this change was that Ivarr wasn't a very significant character and they were able to develop the characters of the Thurgilson brothers.
The television series instead replaced him by introducing the viking brothers Sigefrid and Erik earlier, as in the novel series they only appeared in " Sword Song".