“Outcast” is episode fifteen of season four of Stargate: Atlantis.
Colonel Sheppard returns to Earth, accompanied by Ronon, to attend his father’s funeral, when he is contacted by a scientist. The scientist works for a company that was owned by Henry Wallace, who kidnapped McKay and his sister in “Miller’s Crossing”. Using nannite technology, she and her boss have managed to construct a human-form Replicator – which has now escaped (never a good idea to build these things). Sheppard and Ronon have to track it down.
There is an appearance by former Sergeant Bates, who was in some of the earlier episodes before he was injured by the Wraith.
Although much of the episode revolves around the hunt for the Replicator – with lots of shooting – there is a small side plot related to Sheppard’s family, in particular his brother and ex-wife.
McKay makes a rather awkward attempt to empathise with Sheppard, something he is not that good at. Other than at the beginning, only Sheppard and Ronon of the regular cast have much of a role.