The following contains spoilers and tons of info concerning BSG. Read at your own peril
"This has happened before and it will happen again"
Eighteen months ago Tigh killed Ellen because she betrayed the Resistance, and eighteen months ago she's resurrected on a baseship as one of the Final Five Cylons. The look on her face is utter shock and horror as she discovers what she is, but then, when it all comes back, when her memories return, the real Ellen Tigh stares back at the screen. This women is confident and commanding. But that's not the only reveal.
Cavil walks into the resurrection room to greet Ellen. He knew all along about the existence of the Final Five. She calls him John, named him after her father. He apparently is built like him too. He hates the name, then mocks her and Saul's lack of humanity. Ellen asks him for some clothes before he leaves her.
Twelve months prior to the mutiny we see Ellen and "John" Cavil having a discussion. Cavil notices that Ellen hasn't changed, and she asks him if he's still having nightmares "of dog-faced boys chasing" him in the mist to which he replies that he altered his programming and hasn't slept for 20 years. He's altered some human characteristics, but Ellen notes that he still acts human when it comes to vengeance. Cavil replies that justice requires him to do so.
Just then Boomer walks in, which makes Ellen happy to see a familiar face, until she notices that the 8 is being manipulated by Cavil. She asks her is Cavil has done the swirl yet. (Ew!) Cavil leaves Boomer behind with Ellen so that she'll see the flaws in her maker.
In another scene around the same time, the star by the algae planet goes supernova. Cavil asks Ellen about the Temple of Jupiter which she calls the Temple of Hopes. The people of Kobol built it 3,000 years ago and god showed them the way to Earth. Cavil again mocks Ellen, implying that the temple was a nice trick of Ellen's to reveal the Final Five D'Anna who he had to box. Ellen says that boxing isn't permanent unlike what happened to Model 7. Then Cavil laments that he can't experience the supernova as a true machine. Smell dark matter. He has to experience it in human-like form, and he despises it. He leaves, and Boomer asks Ellen if she feels remorse for what she did to him. Ellen says no. She gave them free will and love, which causes Boomer to ask, who are they to love?
The Resurrection Hub is later destroyed four months prior to the mutiny, and Cavil comes to Ellen asking her to recreate the resurrection technology. The tools are still on the colony. She refuses, stating that she can't do it alone. All Final Five are required. Cavil thinks she's lying and says he'll open up her brain and get the information out that way.
Two days prior to the present, Cavil comes to Ellen and tells her that the Simons will be operating on her. Then Ellen confronts him, revealing how the Five were placed in the colonies. Cavil hoped the Five would become disillusioned with the humans, but the opposite happened. She then says that she knows what he did to Daniel, the 7. He was an artist, and Ellen was close to him, so Cavil messed with the amniotic fluid and corrupted the genetic material, and hence no more 7s. Or so we think. Ellen calls him a sadist, but still loves him. She tries to hug him, but he freaks out and leaves.
Boomer later comes back for Ellen to take her to surgery, but instead of taking her to the Simons, they take off in a raptor and escape, heading for the Galactica.
The bullet wound has given Anders access to his memories. At first he's flashing back through the last few years, but then he starts mumbling about the forgotten. He flashes back to the temple, and mutters that Ellen liked the water as Cottle starts drilling into his brain.
After the first surgery, Anders wakes and he tells Kara that he remembers everything, to get the others, including Ellen. She has to remind him that she's dead. The other three crowd around his bed, asking him questions as he begins to tell them about their lives. The Final Five were scientists living in a research facility on Earth and along with Ellen and Saul, Galen and Tory were lovers. When the nukes hit, they downloaded onto a ship orbiting Earth because they had been warned. They re-invented resurrection. It's called "organic memory transfer" and it came from Kobol, but it fell out of use after the Cylons started to procreated. Ellen brought the system back online. Right then Cottle interrupts them and disperses the group.
Later that day they regroup and Tigh asks why did they go to the 12 colonies. Anders says that they had to warn the other tribes. They knew that the tribes would continue creating artificial life, and the mistakes the 13th tribe might happen to the other colonies. But they didn't have ftl drives, only sublight, so it took them thousands of years, and by then the colonies were in the middle of the first war with the Centurions It happened again. Anders is getting sicker, and Kara wants him to stop, but he brings up the Demetrius, reminding her that if he had answers for her, she would want him to tell her. Kara asks him if he does, and he says that he doesn't, but that he might later. That it's all coming back. He continues by saying that the Centurions had already tried to make human-flesh bodies, the hybrids. The Final Five made a deal with them. End the war and we'll make human Cylons. They made 8, which makes Kara react, and Anders starts to see all of them glow like the five in the Temple of Hopes. Anders ends up having a seizure.
The remaining Three discuss what they've learned. Though they realize they stopped the first Cylon war, Tigh says that they're responsible for the destruction of the colonies. Tory then says that the humans on Kobol created the Five, so they're responsible for everything.
In the meantime, Anders is being prepped for his second surgery by the PC guy. His speech is getting worse, but all Anders is concerned with is telling the others what he knows. Cottle gives Kara the decision on whether to proceed with the surgery, and she gives Anders only enough time as it takes the surgeons to prep him.
Back with the others, Anders tells them that the first model they created was John Cavil. They also embraced the Centurion's religion, that of a single, loving god. They hoped it would end the cycle of violence between Cylons and humans. But Cavil rejected mercy and he suffocated the Final Five. Then he he placed them in the colonies. Back on Earth the Five saw signs that no one else could see. Anders saw a woman. Tory saw a man. Galen thought he had a chip in his head. Kara asks him about the 7, and he replies that the 7 was Daniel. She asks him if he was sure, and Anders says yes. They take him away, and Tigh says they're not done with him yet, while Anders screams at Kara about the Demetrius.
The surgery is performed, and the bullet is taken out. However, no brain activity registers in Anders head.
Around the same time, Tigh goes to his quarters where Caprica Six tells him that the baby, a boy, has started kicking. He doesn't believe it at first, but he rests his hands on her belly, and then feels the movement. The joy of the moment overcomes him.
Though Roslin will remain as President of the Colonies, she informs Lee that it will be a title alone. She's going to let him do all the heavy lifting. Lee needs to pick a new quorum, and he decides that each member should be picked by ship and not colony.
As for Galactica, Tyrol informs Adama that structurally, she's falling apart. Adama, grants Tyrol the title of Chief again, and tells him to fix the ship, but to only use humans. Tyrol realizes that the damage to Galactica is extensive, and goes to Adama again, telling him that they may have to use Cylon technology to fix her. Refusing at first, Adama finally relents.
How did Ellen Tigh pass Baltar's Cylon Detector test?
Why would the 13th tribe abandon resurrection technology?
Can the cycle be broken, or is the fleet doomed to repeat the errors of their ancestors?
Is a Daniel model still alive, and if so who is it?
Is Daniel Starbuck's father?
What is the significance of the opera house?
Is Boomer helping Ellen escape or is she leading Cavil right to the other Four?
What is going to happen to Anders?
Do the Final Five have copies, or rather how do they resurrect?
"Deadlock" airs next Friday.