Very, very good episode

One of the best this season so far

Ok, summary coming up (beware, there is a very big spoiler for this episode at the end. But this is the spoiler thread

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We open the episdode with Zelenka packing some gear in the gateroom, not looking very happy. He's of to M7G-whatever it is (planet from Childhood's End, with the kids) to take a look over their EM field generator. Apparently McKay has decided that Zelenka is the best man for the job, knowing full well what the children are like on that planet. And Zelenka is kinda pissed at McKay

Anyway, up in the control room McKay shows Weir some data from the long range sensors. Two Wraith Cruisers are going past the neighbourhood, and McKay has detected high energy bursts going back and forth between them. McKay thinks that the cruisers are actually trading shots with each other, and that the Wraith are actually doing some serious infighting.
Here we cut to Cheyenne Mountain, where Landry rushes into the breifing room. Agent Barrett from the NID is there and informs Landry that they have recieved intel that a Trust agent has planted a bomb on Atlantis that is set to detonate from a trigger on Earth when Atlantis dials on their next scheduled contact. End of the teaser.
Come back to the Briefing Room at the SGC and Landry and Barrett are informing Dr. Lee of the situation. They need a way to contact Atlantis and tell them there is bomb on the city, and not to dial Earth. Of course, Earth can't dial Atlantis anyway but the Deadalus is conviently returning to Earth on its regular schedule however it is still too far out to contact.
On Atlantis, McKay is telling Sheppard what's going on todays contact report with Earth when they run into Lt. Cadman (the chick from Duet). Seems McKay still has a few issues with her (got UST?

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The infirmary now, and Teyla approaches Beckett with a request to go to the Mainland. Turns Charlin (the old lady that Teyla spoke to in The Gift) has fallen ill, and Teyla wants to know if Beckett will take a look at her, and he quickly agrees.
At the SGC, Dr. Lee has come up with a plan to contact Earth. Send a science team to a planet on the outer edges of the Milky Way and send a message from there to the Deadalus, who can relay it to Atlantis. There's an amusing joke about 101 Dalmations and Lord of the Rings in there (dogs relaying barks and the big bonfires that are lit to inform Rohan of Gondor's plight).
So aboard the Deddy, Caldwell gets the message. But Kavanaugh (he's back! :O) points out that they are too far away from Atlantis to send a message back and they wont be able to get back in range quick enough to inform 'Lantis before they dial Earth. Luckily Hermoid can modify the engines and gets some more speed out of them (and apparently Asgard get annoyed at Kavanaugh too

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So Atlantis is about to dial Earth (litterally about to press the button) when McKay gets the message and stops everything.
In Weir's office McKay proposes to disconnect the ZPM to stop anyone dialing Earth and Weir shuts down all gate activity (Zelenka's team is the only one offworld anyway). Weir and Sheppard hypothesise that the Trust want to blow up Atlantis to ensure that the Wraith never get to Earth or that the Trust operative may be working for the Goa'uld. Ronan of course has no idea what the Goa'uld are and Sheppard explains (apparently he's been doing some reading of SG mission reports, and is up to speed on at least the basics that have happened at the SGC).
Over at the mainland Teyla is speaking with Charlin who knows her time is near and wants Teyla to prepare the other Athosians for the Ring Ceremony. Dieing of natural causes is quite rare among the Athosians (because of the Wraith), and as such they have a ceremony for anyone who has the 'privelige'. Teyla is hesitant to start preparing for the death of the last person she considers family.
Another scene at the SGC with Landy and Barrett with Barrett explaining they raided a Trust warehouse and found out that the trigger is actually on the Atlantis side. And Carter got mentioned - yay

Deadalus relays that message to Atlantis. Caldwell also sends a message back to Earth informing them that Weir wants the Deddy back at Atlantis to assist in the investigation.
At Atlantis, McKay and Cadman are working on some computers in the control room (and he finds out she's an explosive expert and that she can tapdance...) while Weir checks in with Sheppard and Ronan who are sweeping the city for bombs or other suspicous devices. Then the gate starts dialing by itself. It can't actually establish a connection to Earth (ZPM has been pulled) and McKay thinks the Trust agent had it automated as a backup if Atlantis didn't contact Earth on schedule. However he then notices that distress beacon had been actived (gate dialing automatically was a diversion) and that the 2 Wraith cruisers that were flying by earlier have turned around and are heading straight for Atlantis. However they can't figure out why the agent would want to draw the Wraith to Atlantis.
A little scene between Beckett and Teyla where Carson tells her that with the aid of a pacemaker, he could give Charlin a few more years. Teyla is quite relieved to hear that.
Landry's office, and Cheif Harriman aka CHEVRON GUY (WHOOHOOO!!!) walks in and informs Landry that the Deddy has gone back to Atlantis and that they are out of contact.
Now to Weir's office and she's looking through passenger manifests for the Deddy as Shep walks in. She's doesn't like the fact that they have to suspect one of their own. Shep raises the point that it could be someone on Atlantis as well, not just the Deddy. McKay comes in and names Lt. Cadman as a suspect (she's an explosive expert, just happened to be stay behind on Atlantis this time and she's always around when things happen). Shep disagrees saying she's one of his most trusted officers in his command. Cadman rocks up at that point to inform Weir that the Deddy has landed.
Walking through the Deddy, Caldwell tells Weir he wants to start the interrogations immedaitely. Weir shuts him down, saying that this falls under Atlantis jurisdictions.
Cut to a scene of Weir questioning Kavanaugh. He's fairly indignant that Weir would suspect him, commenting on how she has a personal grudge against him. Weir details some suspicous activities of his (requests to leave the city after the Seige, then a request to come back before he suddenly wanted to leave again - just before the whole bomb incident). Kavanaugh denies everything. He also has a little dig at Weir's command ('no need for the Trust to blow up Atlantis when Dr. Weir is command' (ie, she'll end up destroying it through poor command))
Over on the Mainland, Teyla is telling Charlin about how Dr. Beckett can give her a few more years. Charlin will have none of it, saying she is prepared to go. Teyla is saddened that when Charlin dies, she will be alone but Charlin tells Teyla that her people (the Athosians) are her family as well, and they will need Teyla's strength.
Weir is now questioning Dr. Novak (hiccup lady on the Deddy) who points the finger at Kavanaugh.
Over to the control room, McKay has figured out that there is no actual bomb. What the Trust agent has done is to override some failsafe mechanisms that govern power flow out of the ZPM, so that the ZPM will explode when a heavy use of it occurs. Like dialing another galaxy. Or like activating the cloak, which they will now need to hide from the Wraith cruisers that are en-route. Which is why the distress beacon got activated. The agent also put in some command codes to stop anyone from re-activating the failsafes. McKay thinks he can shut down some secondary systems so he can active the cloak, but stop the ZPM from overloading.
Weir tries to get some more info out of Kavanaugh, but hits a blank wall. In her office, Ronan offers his assistance in getting Kavanaugh to spill the beans (read torture). Weir and McKay are reluctant to resort to it, while Sheppard and Caldwell think its a good idea.
In the infirmary, Beckett and Teyla are by Charlin's bedside as she says her last goodbye to Teyla. Teyla is saddened by her passing, shedding some tears.
So the Wraith are on the way and they have no choice but to plug the ZPM in, activate the cloak and try and maintain power levels to stop the ZPM from overloading. So things are going well, until the City's inertial dampeners (part of its Star-Drive) turn on which causes power levels to spike rapidly. The ZPM is going to overload unless they can reactivate the failsafe mechanism. They start planning an evacuation of the City via the Deddy and puddle-jumpers. McKay points out that if they had the command codes, they could stop the overload in a couple of minutes. Weir relents, and gives Ronan the ok to use torture on Kavanaugh. This starts of the final (and best) scene.
Teyla and some Athosians are preparing Charlin for the Ring Ceremony. Beckett points out that they are about to evacuate, but Teyla knows this and will complete the ceremony then board the last puddle-jumpers. She's dressed in a formal dress that looks quite splendid on her

Some traditional Athosian music begins to play (think native, stringed and wind instruments) and Teyla begins to sing for the ceremony. Cut to a montage (with Teyla's song still going) of McKay working to prevent the overload, Weir looking concerned in her office, the Wraith Cruisers approaching the planet. McKay looks glum as he announces 10 minutes to the overload and Cadman comes up to him and Weir saying she has found something. More shots of Teyla singing (Rachel Lutrell has a lovely voice), then one of Sheppard running to stop Ronan's interogation. Kavanaugh is unconcious on the ground as he fainted before Ronan could touch him
On the bridge of the Deddy, Caldwell informs Weir that he is ready to depart when he gets beamed down to Atlantis. He's confused and angry to find Sheppard and Weir who confront him and demand the access codes

The something that Cadman found was Caldwell's authorisation code to access the City's operation system (to auto-dial the gate, activate inertial dampeners etc). Weir accuses him of working for the Trust at which point Caldwell's eyes flash. He's been Goa'ulded. Ronan gets into a little scuffle with Goa'uld and Sheppard pulls out a taser which he zaps the Goa'uld with. After a little while, he manages to repress the Goa'uld symbiote enough to bring Caldwell out (much like O'Neill did with a Zat to Skaara) who is able to give Sheppard the command codes. Sheppard rushes them to McKay, who is able reactive the failsafe mechnisms and stop the overload. The city stays cloaked and the Wraith Ships move off, none the wiser. And Teyla finishes her song
Some housekeeping at the end - Hermoid is making the final calculations to use the Asgard beam to beam the symbiote out of Caldwell (I remember someone a while ago wondering if that was possible - looks like that is

). Zelenka comes back
extremely peeved off at McKay, as the children have braided his hair, coloured it and painted his face. McKay is smug

Then Weir at the end is torn over her descision to allow the torture (though it didn't actually happen) of Kavanaugh go ahead. Shep attempts to justify it, and then Weir closes the episode by remarking 'Here we are gloating over the in-fighting among the Wraith - how are we any different?'
And thats it, the end

Now I'm going to bed 'cos I'm tired