The Daedalus arrives to defend Atlantis from the Wraith onslaught, but it may not be enough when the team discovers that an even larger armada is on the way.

An Air Force pilot attempts to reassemble SG-1 after they have gone their separate ways. An old "friend" arrives on Earth asking for Daniel's help in finding an ancient treasure and she won't take no for an answer.

An Ancient communications device renders Daniel and Vala unconscious, sending their minds to another galaxy where they inhabit the bodies of two people persecuted by the followers of an evil religion.

Daniel comes face to face with the Ori, a fiery race of beings who demand the worship of mortals. Elsewhere, Stargate Command encounters the first Ori missionary in our galaxy.

The Daedalus is infected by a Wraith computer virus, while members of the expedition hope to return to Earth.

Sheppard and his team attempt to locate Lieutenant Ford, only to find themselves captives of a former soldier who is being hunted by the Wraith.

Jackson and Mitchell must join Vala on an interplanetary scavenger hunt when they learn that they are still bound together by an alien energy field.

A run-in with a Wraith Dart leaves the consciousness of a precocious Atlantis security officer trapped in Dr. McKay's mind.

SG-1 visits a world whose people once worshiped Vala as a god and demand that she stand trial when she confesses to manipulating them.

The Atlantis team finds a culture that lives in relative safety from the Wraith, because they hand over their criminals to the Wraith and crash-land in the volatile penal colony.

Samantha Carter returns to Stargate Command when the Ori seize control of a planet, using an expanding force field in an attempt to gain a foothold in our galaxy.

McKay puts the team at risk when he tries to perfect unfinished Ancient technology that wiped out a civilization. Ronon Dex discovers that he is not the lone survivor from his world.

SG-1 must investigate when evidence suggests that there are still Goa'uld hiding on Earth including a former System Lord. Tensions between Earth and the Free Jaffa continue to mount.

The team discovers a young Wraith girl who has been raised by a human, and is in hiding from the people of her human village in fear of her life.

Colonel Mitchell is injured in a skirmish with a warrior from a mythic tribe of rebel Jaffa, and is trained in their fighting techniques only so that he may engage in a ritual battle to the death.

Colonel Sheppard begins to undergo a disturbing physical transformation after being exposed to Beckett's anti-Wraith drug.

SG-1 finds a genetically advanced Goa'uld-human hybrid created by Anubis, and returns him to Earth for study. But even keeping him alive may not be worth the risk.

When the team finds an Ancient warship adrift on the edge of the galaxy, its crew still alive, Colonel Sheppard enters their virtual reality stasis to communicate with them.

Earth is infected with a deadly Ori plague, prompting an ally from SG-1's past to come to their aide. Gerak proposes that the Free Jaffa follow the Ori religion.

As the Ori plague spreads rapidly, SG-1 hopes that the Prior who caused the disease may hold the key to its cure. Gerak tries to rally the Jaffa to the Ori's cause, prompting Teal'c and Bra'tac to initiate a resistance.

The team is captured by the missing Lieutenant Ford, who is now leading a group of young men who are taking the Wraith enzyme and who wants the team's help in a suicide attack against a hive ship.

Colonel Sheppard and his team find themselves prisoners of the Wraith following Ford's attack on a hive ship. Dr. McKay goes to great lengths to help them.

Colonel Mitchell stands falsely accused of murder but he remembers committing it, thanks to technology that grafts memories into someone else's mind.

Sheppard finds himself on a planet where time passes more rapidly, with no way to contact his team or return to Atlantis.

Multiple SG-1s show up at Stargate Command, leading the "real" team to conclude that they have each been inadvertently displaced from different parallel realities.

When an operative of the Trust plants a bomb in Atlantis, the team must find a spy within their own ranks before the Wraith arrive and discover the city.

Baal kidnaps Teal'c as part of a plot to brainwash those Jaffa advocating a move toward democracy. Cameron Mitchell learns that an old friend is about to die.

When Dr. McKay is trapped underwater in a sinking Puddle Jumper, his only chance for survival may be an hallucination of Samantha Carter.

Daniel is imprisoned on a world under the influence of the Ori, and the Prometheus is caught in a firefight when SG-1 tries to rescue him.

The team finds a world that possesses Ancient defense technology, where Colonel Sheppard finds himself a pawn in the rivalry between the heirs to the throne.

SG-1 is captured after a deal with the Lucian Alliance goes bad and the planet's Stargate goes missing. Meanwhile, a former System Lord attempts to rebuild his empire.

The team discovers two pods that contain the minds of alien beings, who take control of Weir and Sheppard's bodies to continue their personal war.

A tour of an off-world research base for a group of foreign diplomats turns dangerous when an insidious insect species gets loose.

After a team from Atlantis goes missing, the expedition finds itself in the middle of a Genii coup.

Mitchell and Carter are shifted to another dimension, making them invisible to everyone at the S.G.C. Meanwhile, Teal'c and SG-9 discover that the Sodan have been brutally attacked.

An amnesiac young Lieutenant in Atlantis suffers from disturbing nightmares that he is a Wraith, only to make a shocking discovery about himself.

Vala Mal Doran makes contact with Stargate Command from the Ori home galaxy, and tells the story of her life undercover in a village of followers building the Ori's invasion fleet.

Sheppard's team meets a civilization about to be destroyed by a super-volcano, and is trapped there when the Stargate is destroyed during the evacuation.

SG-1 discovers the village of Camelot on an alien world, and must face Merlin's security system when they go in search of an Ancient weapon. Elsewhere, Earth and its allies assemble a fleet when a working Ori Supergate is discovered.

Michael and his Wraith faction arrive at Atlantis to propose an alliance, hoping to use the retrovirus to transform their Wraith enemies into prey.