Stargate Atlantis returns for an action-packed fourth season with the team welcoming new members and battling enemies new and old. Following the dramatic finale of season three, the courageous Lt. Col. John Sheppard (Joe Flanigan) and the brilliant Dr. Rodney McKay (David Hewlett) and the rest of the team is working together to save their leader, Elizabeth Weir (Torri Higginson). The team must find a new home for the city and defend it against the continuing threat of the Wraith and the Replicators. Season 4 also sees Lt. Col. Samantha Carter (Amanda Tapping) and head of medicine Jennifer Keller (Jewel Staite) join the Atlantis expedition. While Ronon (Jason Momoa) is confronted by his past, Teyla (Teachel Luttrell) is forced to question her role and her people's future.
Together, the Atlantis team must confront its standing enemies, forge new alliances, and delve deeper into discovering the mysteries of the Pegasus Galaxy.