Code Name Eternity - Complete Series

Ethaniel, an alien creature from a distant galaxy, takes on human form in order to capture the rogue alien David Banning. Now Ethaniel must learn about our world: how we think and how we relate to each other. Dr. Laura Keating assists Ethaniel in his understanding of the "human" way while he pursues Banning. Ethaniel knows Banning's secret goal lies in the brain of Thorber, Ethaniel's missing brother. A brilliant scientist, Thorber originally worked with Banning but fled after discovering Banning's real scheme: the ultimate destruction of all human life on earth. Joined by Byder, a rebel hooked on conspiracy theories, Ethaniel and Dr. Laura Keating set out on their mission. Forging a powerful interspecies alliance, Laura and Ethaniel risk their lives.

http://www.imdb.com/title/tt0190174/plotsummary