Complete story — includes the ending
Kevin goes on a crusade to find an escaped alien named Ragnarok in order to avenge his father Devin Levin's death. Ben and Gwen learn about Kevin's past from Max, who was Devin's partner in the plumbers, where they also accompany Kevin. The trio learn about Ragnarok's plan of destroying the world by draining the sun rays. Leaving Ben and Gwen, Kevin manages to foil Ragnarok's plan and finishes him, thus avenging his father's death.
Sources and content license
Source and revision history · Adapted from Wikipedia contributors, List of Ben 10: Alien Force episodes. HTML formatting and reference markers removed. · Content license