When Hiccup and Toothless discover an ice cave that is home to hundreds of new wild dragons and the mysterious Dragon Rider, the two friends find themselves at the center of a battle to protect the peace.
Ex-government operative Bryan Mills is accused of a ruthless murder he never committed or witnessed. As he is tracked and pursued, Mills brings out his particular set of skills to find the true killer and clear his name.
An imperial guard and his three traitorous childhood friends ordered to hunt him down get accidentally buried and kept frozen in time. 400 years later passes and they are defrosted continuing the battle they left behind.