Vikings, Season 4, Volume 1 DVD. Take another gripping voyage into the ruthless world of Vikings, with its thrilling action, powerful performances and intriguing story line. King Ragnar returns from battle gravely ill. Disheartened by his marriage to Aslaug and challenges with his sons, Ragnar seeks companionship with his slave Yidu. Meanwhile, a defiant Rollo remains in Frankia, Queen Kwenthrith plots to reclaim Mercia, and the enigmatic Harald Finehair appears. Ultimately, Ragnar and Rollo engage in a merciless battle to define their legacies.   $15.