Here below an episode list of Stargate Atlantis Season 5:
SGA S5xE01 Search and Rescue (Part 2)
Carter launches a rescue operation for several victims of a huge off-world explosion, but the rescue party must also combat Michael and his army who also wish to recover the survivors. Captain Alicia Vega joins the expedition.
SGA S5xE02 The Seed
Dr. Carson Beckett is removed from stasis because he's the only one who can take action to figure a way out of a serious dilemma before it’s too late for some of his close friends. Paul McGillion will guest star as Carson Beckett.
SGA S5xE03 Broken Ties
Ronon is reunited with Tyre, a former Satedan warrior turned "Wraith worshiper" (from episode S4x03 "Reunion"). Apparently having turned on his new masters and broken free of their brainwashing, Tyre hopes to rebuild the relationship with Ronon and Atlantis that has been destroyed.
SGA S5xE04 The Daedalus Variations
The Daedalus appears in orbit, abandoned. The expedition know that the Daedalus is currently at Earth, and decide to investigate. They soon discover this ship is not the one they know, and that it is jumping between different realities.
SGA S5xE05 Ghost in the Machine
The Atlantis team is surprised when a Replicator scientist, named Koracen, reveals that they have developed a way to "digitally" ascend. Skeptical by the revelation, Koracen demonstrates the procedure, which locks the team out of one of the rooms in the city. Desperate to gain entry, Sheppard orders the door be blown apart, however, just as they are about to, the door opens to reveal a friendly face.
SGA S5xE06 The Shrine
Rodney McKay begins suffering from the Pegasus Galaxy equivalent of alzheimer's disease, and reverts to a child-like state. (This episode will be the 300th stargate episode.)
SGA S5xE07 Whispers
Sheppard and Beckett join Maj. Anne Teldy’s team on a planet with one of Michael’s research facilities for the early versions of his human-iratus hybrids concealed inside a cave system. Unfortunately for them, Michaels hybrids are nearby conspiring against them. Paul McGillion will guest star as Carson Beckett.
SGA S5xE08 Tracker
The team comes to the aid of a village under Wraith threat, but Ronon and McKay must rescue one of their own when Dr. Keller is kidnapped...
SGA S5xE09 The Queen
Teyla is posing as Todd's (Christopher Heyerdahl) Wraith Queen, giving him the authority to enter talks with another hive and its Queen. It's not to long before suspicion is cast upon them and they must work together to maintain their ploy...
SGA S5xE10 First Contact (Part 1)
Daniel Jackson returns to Atlantis to do research on the Lantean scientist Janus. The Atlantis Expedition makes first contact with a new alien species. Michael Shanks will guest-star as Daniel Jackson.,
SGA S5xE11 The Lost Tribe (Part 2)
Sheppard must race to save McKay and Daniel Jackson from an Ancient laboratory before the Wraith Todd, who has hijacked an Earth battle cruiser, gets there first.
SGA S5xE12 Inquisition
The Atlantis expedition is put on trial for the crimes against the Pegasus Galaxy by a group of human civilizations that have formed 'The Coalition'.
SGA S5xE13 Outsiders
Sheppard and his team meet a man and a woman named Sefaris and Novo who have become immune to Wraith feeding process through the Hoffan Drug and a people called Balarans who have welcomed them to their community. However the Balarans are threatened when the Wraith come hunting for the two 'outsiders'.
SGA S5xE14 Prodigal
In search for Teyla's baby, Michael and his hybrids infiltrate Atlantis. While the hybrids take control of the city's systems one by one, it's up to Sheppard's and Lorne's teams to retake the city. But first McKay has to disable a seemingly impenetrable stun energy field setup by Michael.
SGA S5xE15 Remnants
John Sheppard has been abducted. After freeing himself from his bonds, he soon discovers who it is who tied him up: Acastus Kolya (Robert Davi). In Atlantis, Woolsey, McKay, and the rest of the team are about to make a shocking discovery about an ancient race.
SGA S5xE16 Brain Storm
Rodney McKay is invited to a landmark scientific presentation by an old rival from his school days. It appears to be a weather-control device but then everything goes wrong.
SGA S5xE17 Infection
The team investigates mysterious things happening on board a Wraith Hive. Meanwhile, Dr. Keller is doing research on Wraith physiology.
SGA S5xE18 Identity
Dr. Jennifer Keller is diagnosed with a psychological ailment. However, little does the Atlantis expedition realize that she has been exposed to body-switching technology that does not require the subjects to be in close proximity. Meanwhile Keller's consciousness faces a desperate struggle for survival inside the body of a wanted fugitive woman named Neeva.
SGA S5xE19 Vegas
Detective John Sheppard and IOA Agent Richard Woolsey find themselves in the midst of a CSI like murder case involving several killings apparently of Wraith origin in Las Vegas, Nevada. This episode will be filmed in Las Vegas, with filming for the season ending there, but it will air as the 19th episode.
SGA S5xE20 Enemy at the Gate
No plot details have been revealed. This milestone episode will not be a comedy episode, but the producers have "something big in mind". This milestone episode is also the final episode of Stargate Atlantis and will not end on a cliffhanger. It will not be a comedy episode, but "much of the cast will wear funny hats" It will be shot in the 19th slot.
An official summary of Enemy at the gate has been released:
SGA S5xE20 Enemy at the Gate
Todd contacts Atlantis and reveals that a Wraith subordinate has managed to acquire several Zero Point Modules that he has used to power a formidable new hive ship. He urges Woolsey to attack and destroy before it becomes a threat to Atlantis.
On board the Daedalus, Colonel Caldwell, Colonel Sheppard and the rest of the team, rush to engage the new hive ship. But the Z.P.M. powered vessel proves itself an impressive opponent, crippling the Daedalus before making a sudden and inexplicable jump into hyperspace.
Puzzled over the Wraith's sudden departure, the team picks up a weak subspace signal in Wraith code. McKay is quick to recognize that the communique was sent, through subspace, from another reality. Once deciphered, their worst fears are realized. The Wraith message contains a familiar set of coordinates. The hive ship is on its way to Earth!
We now have the full Stargate Atlantis Season 5 Episode List but if we get more details we will update it.
This 20th episode is not yet the end of Stargate Atlantis though: it will be continued by a 2-hour movie later in 2009, and maybe more if it is still successful!