The second season of Stargate: Atlantis was a period of exploration for the members of the Atlantis expedition. Though Rainbow Sun Francks, playing Lt. Aiden Ford left the cast, Jason Momoa joined as the character of Ronon Dex was created, and Paul McGillion, playing Dr. Carson Beckett, was upgraded to a regular character. Plot-lines from the first season were continued and expanded upon, and the season ended with Atlantis, and Earth, in a dangerous predicament.