Season four of Stargate Atlantis, an American-Canadian television series, began airing on September 28, 2007 on the US-American Sci Fi Channel. The fourth season concluded after 20 episodes on March 7, 2008 on Sci Fi. The series was developed by Brad Wright and Robert C. Cooper, who also served as executive producers. Amanda Tapping joins the cast as a regular for 14 episodes, Jewel Staite was a recurring character for eleven episodes, while regular cast member Torri Higginson was a recurring cast member for four episodes. Other season four regular cast members include Joe Flanigan, Jason Momoa, Rachel Luttrell, and David Hewlett.
During a visit to New Athos, Teyla and Dr. Keller find themselves on the run from a primitive tribe of warriors.
When an alarm sounds throughout the city, initiating a quarantine lock down, the Atlantis team finds themselves trapped in various sections of the city.
Wanting to maintain diplomatic relations, Sheppard and McKay agree to accompany a precocious young princess on a rite of passage.
When he learns of his father's passing, Sheppard becomes involved in a covert experiment which has unleashed a human-formed Replicator in the city, upon his arrival back on Earth with Ronon.
During an off world mission, Carter, McKay and Dr. Keller become trapped in an underground mining chamber rocked by fierce seismic tremors
When Ronan Dex is scheduled for a suitability review by the IOA, Teal?c travels to Atlantis to counsel him.
As Teyla continues to search for her people, a mysterious new illness sweeps throughout the galaxy, killing scores of people.
An old friend's unforeseen return spurs a race against time to rescue a missing teammate.
Following another unsuccessful search for Teyla, Lt. Colonel Sheppard returns home to Atlantis to find the city completely abandoned.