3x08 McKay And Mrs. Miller

Rodney McKay (David Hewlett) is called back to earth to convince his estranged sister, Jeannie Miller, to assist the Air Force in implementing an important mathematical proof that has application to one of McKay's experiements. Having not seen her in four years, McKay finds it difficult to pry Jeannie away from her family, so he has no choice but to disclose the existence of the Stargate program to her.

McKay and Jeannie travel to Atlantis, and begin the experiment, which is intended to generate limitless energy by bridging parallel universes. The experiment is initially successful, until a Rodney McKay from the parallel universe appears in the experiment's containment chamber asking the team to shut down the experiment to avoid damaging his universe. And this Rodney MKay, preferring to be called "Rod", is the polar opposite of our McKay, with charisma, courage, and humility in spades. Rod forms an instant bond with Jeannie and the other members of the Atlantis team, causing McKay to become instantly jealous.

While at first believing the crisis to be averted, the team soon realizes that shutting down the experiment from their end won't prevent ROd's universe from being destroyed. And what's worse, people in Rod's universe have a plan to save their own universe at the expense of ours. Now Jeannie, McKay and Rod must find a way to save both universes, and may have to make certain sacrifices in the process.

Text by Stargate.MGM.com