|Atlantis Season 2|
|Season 1||Season 3|
The NID pick up intelligence that The Trust has not only heard of Atlantis, but has been there, and the Goa'uld has planted a bomb in the city that is sent to go off the next time the expedition dials Earth.
Lt. Colonel John Sheppard meets with Dr. Radek Zelenka in the Gate room aboard Atlantis. Zelenka is being sent to M7G-677 ("the planet with all the kids") to repair their Electromagnetic field generator. Zelenka however, is not happy; he does not like children. Meanwhile, Dr. Rodney McKay radios Sheppard, Dr. Elizabeth Weir and Ronon Dex to show them two Wraith cruisers he has discovered near Atlantis, but not on their way to the city. They are actually shooting at each other.
At Stargate Command, Major General Henry Landry is visited by Agent Malcolm Barrett, who informs him that The Trust is now controlled by the Goa'uld and that they have planted a bomb in Atlantis, which will explode the next time the Atlantis expedition dials Earth – which is scheduled for later that day. Landry orders Dr. Bill Lee to quickly find a way to warn them.
Back in Atlantis, McKay meets Lt. Laura Cadman again but feels uneasy around her, due to a previous situation. Meanwhile, Teyla Emmagan asks Dr. Carson Beckett to accompany her to the mainland to examine her old friend Charin who is very ill. They do so and Charin asks Teyla to prepare the Ring Ceremony, which is used to celebrate the natural death of a person.
On Earth, Dr. Bill Lee discovers a way to contact Atlantis by using a small planet at the edge of the Milky Way galaxy and the Daedalus as relay points. They are able to contact the Daedalus, which then relays the warning message just in time to prevent Atlantis from dialing the Stargate. Afterward, McKay disconnects the Zero Point Module while teams search the city for explosives. Unfortunately, they find nothing. The Daedalus is also called back to the city to help find the saboteur; but before this happens, they relay another message to Atlantis. Suddenly, Atlantis' Dial Home Device begins to dial Earth on its own but can not establish a connection due to insufficient power. As if in response, the city's transmitter sends a beacon to the nearby Wraith cruisers, alerting them to Atlantis. The city will have to be cloaked again.
Later, Weir begins an inquiry to find out who planted the bomb and when the Daedalus returns, she questions Dr. Peter Kavanagh who was aboard the ship. Kavanagh, however, reasons that he is the main suspect because Weir is being driven by emotions. Next, Weir questions Dr. Lindsey Novak but during the inquiry, McKay has made a discovery: there is no bomb. In truth, the fail-safe of the ZPM was deactivated and blocked with a code, thus causing a massive overload in the device if enough energy is supplied. They now have a dilemma, they need the ZPM to cloak the city. Weir questions Kavanagh a second time, but he does not say anything. She then discusses the situation with the senior staff and Ronon hints at torturing the code out of Kavanagh as a quick solution; however, Kavanagh immediately faints under threat from Ronon.
Meanwhile, Teyla evacuates her people back to Atlantis and also tries to persuade Charin to let herself be treated by Beckett; however, Charin is accepting of her fate to die a natural death. She is later brought to the Atlantis infirmary and although Beckett wants to treat Charin, Teyla persuades him to let Charin die.
The Wraith have appeared above Atlantis and the city must be cloaked to avoid detection. However, the Inertial dampeners of the city suddenly activate which causes the ZPM to overload. Atlantis will be destroyed in roughly 30 minutes. The senior staff then decides to evacuate the people of Atlantis to a planet in the same solar system where they found the crash-landed Wraith ship and it is at this point that Dr. Weir authorizes the torture of Kavanagh. While all the preparations are being done for evacuation, Teyla and Beckett conduct the Ring Ceremony for the dead Charin, during which Teyla sings for her.
Ten minutes before the ZPM would have overloaded, Cadman informs Weir and McKay that she discovered that Colonel Steven Caldwell was responsible for everything. When they question Caldwell, they find that he is a Goa'uld. Ronon subdues Caldwell and Sheppard uses a Taser on him, allowing Caldwell to momentarily take back control and give the team the fail-safe code. McKay enters it into a console and the overload is averted.
Later, McKay informs Beckett and Cadman that Hermiod plans to use the Asgard transporter beam to remove the Goa'uld symbiote from Caldwell; the next episode shows that Hermiod does this successfully. Zelenka has also returned from M7G-677, face painted, hair beaded, and in a foul mood. Weir talks with Sheppard and questions her decision in handling Kavanagh, but Sheppard reassures her that she only did what she had to do.
101 Dalmatians; Asgard; Asgard transporter; Athosian; Atlantis infirmary; Bomb; Brainwashing; Lt. Colonel Samantha Carter; Cloak; Daedalus; East Pier; Electromagnetic field generator; Failsafe mechanism; Funeral; Goa'uld; Goa'uld attempt to destroy Atlantis; Grounding station; Heart; Inertial dampener; Lantea's mainland; Life support; The Lord of the Rings; M7G-677; Mr. Mom; Naquadah generator; P4M-399; Pacemaker; Particle magnum; Puddle Jumper; Ring Ceremony; Stardrive; Tuttleroot soup; Pocket watch; Power distribution center; Taser; The Trust; West Pier; Wraith; Wraith civil war; Wraith cruiser; Zero Point Module
Lee: What about the Daedalus? It's on a return voyage to the Milky Way. We could use them to relay the trans... Ah, no, I mean, wait. God, there's no way they're close enough, even with their long-range transmitters.
Landry: You'll find another way to get the message to them.
Lee: I will?
Landry: Course you will. It's what I pay you for.
Landry: I thought you said the Daedalus was too far away for our transmitter to reach.
Lee: It is, which is why we have to get closer. P4M-399, it's a, it's a tiny little planet right on the very outskirts of our galaxy, but if we can send a science team there through the Gate, they should be close enough to relay the information to the Daedalus and then they can -- it's, it's, it's like the Twilight Bark... (blank stares from the rest of the room)... Twilight Bark? Hundred and One Dalmatians? Didn't you guys see that movie? My kids love it. Any-- well ok, so there's all these dogs and one barks here, one barks here, one -- they, they, they send a message across the countryside...(silence)... Lord of the Rings. (everyone begins to nod in collective understanding and start murmuring) Lord of the Rings, you know when they light all those signal fires on the mountaintops. You saw that, right? So okay.....
Landry: People, people. I believe we have work to do
Hermiod: Dr. Kavanagh?.
Hermiod: Stop talking, please. (Silence) Thank you.
Weir: How many offworld teams do we have out there?
McKay: Just Zelenka and his team, on M7G677.
Weir: Well, unfortunately, he's gonna have to sit tight until we sort this thing out.
Sheppard: Stuck with all those kids.
Ronon: What's a Goa'uld?
Sheppard: It's a slimy, snake-like alien creature: burrows into people's heads and takes control of their bodies.
Ronon: That doesn't sound pleasant.
Kavanagh: You don't have the…strength to be leading the fight against the Wraith.
Weir: If I'm remembering correctly, you're the one who wanted to, what was it? Run and hide?
Kavanagh: And at the time, I was right! If the Daedalus hadn't arrived at the eleventh hour, this city and everyone in it would have been wiped out, because of your recklessness. There's no need for the Trust to blow it up when Dr. Weir is at the helm.
Caldwell/Goa'uld: I warn you - as a Goa'uld I now possess the strength of many men.
Ronon: Won't be a fair fight then.
Sheppard: Did you see Zelenka?
Sheppard: You should take a quick look before he washes his face. The kids did a real number on him.
- An early draft of "Critical Mass" did not include Lt. Laura Cadman, but instead a scientist named Dr. Alison Seagle, who was part of a subplot where McKay comes to her defense after Sheppard begins to suspect that she is the traitor.
- This is the first and only episode of Stargate: Atlantis to feature the Goa'uld, the primary antagonists during the first eight seasons of Stargate SG-1, though they were mentioned in earlier episodes. It's also the first episode multiple team members, namely Ronon Dex and Teyla Emmagan, hear about the Goa'uld, which is addressed by Ronon asking "What's a Goa'uld?".
- This episode shows that Colonel Steven Caldwell has been under the control of a Goa'uld for an unknown period of time which may explain his hostile attitude in earlier episodes. Indeed, he displays a somewhat friendlier attitude after being freed. He is shown to have been controlled for at least a couple of months, long enough for a trip from Earth to Atlantis, back to Earth, back to Atlantis and at the beginning of the episode be on a return trip to Earth. This is because Weir states the Goa'uld copied the Atlantis operating system, returned with it to Earth where the Trust's Goa'uld scientists altered it and then he brought the altered program back to Atlantis.
- This episode shows that shooting a Goa'uld with a taser can injure it enough for its host to regain control for at least a few minutes. A Zat'nik'tel was used to similar effect on Klorel in Skaara's body in "Within the Serpent's Grasp".
- When trying to devise a way to send a long-range message to Atlantis, Dr. Bill Lee sets up a relay system and makes a reference to the "Twilight Bark" from 101 Dalmatians. Nobody gets the reference, so he uses Gondor's signal fires from The Lord of the Rings as an example and they all nod enthusiastically.
- When Teyla Emmagan sings in the Ring Ceremony scene, the actress, Rachel Luttrell, is actually singing. The song is "Beyond the Night" which was written by Joel Goldsmith, composer of the majority of music heard in the Stargate series' including the themes to Stargate: Atlantis and Stargate Universe, and his sister Ellen. In the audio commentary with Martin Wood and Rachel Luttrell, they explain that she flew to L.A. to record the song but had to redo it because it sounded like it was recorded.
- This is the first appearances of Stargate SG-1 recurring characters Agent Malcolm Barrett (Peter Flemming) and Dr. Bill Lee (Bill Dow) on the series.
- A portion of the naquadah reactor with the key pad appears to be part of the original naquadah reactor loaned to the SGC from the Orbanians in the Stargate SG-1 Season 3 episode "Learning Curve".
- Elizabeth refers to the events of the Stargate SG-1 episode "Full Alert" and "The Siege, Part 1", Dr. Kavanagh refers to those of "The Siege, Part 3" and John refers to those of "The Defiant One".
- As in the Stargate SG-1 episode "Prometheus Unbound", Dr. Novak suffers from hiccups while nervous.
- Lt. Laura Cadman is in the United States Marine Corps, so her hair should either be cut (like Lt. Colonel Samantha Carter's) or tied up at the back rather than left hanging down when she is on duty. However, it has been stated, (by both Carter and Woolsey) that the rules are more relaxed on Atlantis.
- At the beginning of the episode, Dr. Bill Lee states that the Daedalus left Atlantis one week prior on a return trip to Earth; however when recalled to Atlantis, the Daedalus arrives within a day as evidenced by the wraith cruisers which Dr. Rodney McKay stated were one-one and a half days from Atlantis. Given the lengthy time travel takes between galaxies, the Daedalus would not have been able to make it back to Atlantis before the arrival of the cruisers, thereby allowing the bomb to detonate.
- When explaining his plan to transmit a warning to Atlantis, Dr. Bill Lee uses the Earth's point of origin symbol to identify Atlantis on the whiteboard. This could, however, be because the symbol has a distinct letter-"A"-like appearance.
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