The fourth season of Stargate: Atlantis began airing on Sci-Fi Channel in the US on September 28, 2007. This season, it moved to a new timeslot: 10:00pm Eastern/Pacific time, 9:00pm Central. The premiere, "Adrift", picks up seconds after the events of "First Strike", the season 3 finale. Torri Higginson and Paul McGillion are no longer regulars in season four, and Amanda Tapping joins the cast, carrying the role of Colonel Samantha Carter over from Stargate SG-1.