galadriel1010 | Journey's End Theories. SPOILERS ALERT

<lj-cut text="cut for length">The darkness is coming, the terrible crushing silent darkness of six months without Doctor Who. Yes, it’s that time, it’s the end of the series and it’s a massive one. Journey’s End is 65 minutes of explosions, deaths and explanation, or so we hope. It’s all shrouded in mystery until tomorrow night, because there are no preview tapes and no leakages. All we have is rumour and theory. So here I have a compilation of the best big questions and the most likely theories to answer them.

What is the Osterhagen Key?

Just before she teleported out of New York, courtesy of UNIT and the Sontarans, Martha was given a little boxy thing called the Osterhagen Key. Even Captain Jack with his seemingly endless supply of soldiers in bars doesn’t know what it is, but Harriet Jones, former Prime Minister (yes, we know who you are) does know what it is. She isn’t telling though, she just tells Martha not to use it under any circumstances. So what is it? Some of the best theories (my notes in italics):

A suicide weapon which will destroy the Earth and take the dalek army with it. Unlikely, because the UNIT commander said it should be used to protect the future of the human race, and there wouldn’t be one if it’s a suicide weapon.
Something relating to the Valeyard, it translates as Boneyard or Graveyard, which were both insults that the sixth Doctor used for the Valeyard. The Valeyard was an evil future incarnation of the Doctor created by the Timelords in order to convict him in Trial of a Timelord. Very interesting. We shouldn’t be getting to the Valeyard yet, as it was between his twelfth and thirteenth regenerations, but it could be coming a bit earlier, especially as that regeneration came as a complete shock and we know it can’t be real… can it?
A device to return Earth to its original position. It’s an anagram of Earth’s Gone, so this is possible. Harriet Jones may be dead-set (no pun intended) against using it because it could create an enormous paradox and destroy the universe. Which would not be good.
A device to create a cloned Earth. Doctors Oster and Hagen are biologists, who I believe are working in cloning, but I could be wrong there.

Who is “the most faithful companion”?

Dalek Caan, now driven insane by his foray into the Time War, predicts “Everlasting death for the most faithful companion”, and Davros tells us that he speaks only the truth. If this is the case, who is the one to die.

Captain Jack Harkness: The Captain can’t die, he just can’t, so death for him would be temporary… Unless he gains the ability to die permanently, which would make Torchwood more interesting next year, would he tell them, or would they go on thinking he can’t die only for him to die in Ianto’s arms. Did I mention that I love the Jack/Ianto relationship? Well there it is, I do. Back on subject, Jack is immortal, cannot be killed by anything so he’s unlikely all things considered
Rose: Very faithful, she’s crossed universes to be with the Doctor. Hints suggest that she’s not going to be around for the specials, and wouldn’t her death be dramatic if she’s only just been reunited with him? Billie says she’d love to return, so it sounds like she’s safe but not staying
Martha: Stuck with him despite the fact that she loves him and he was clueless, that’s pretty faithful, but she’s engaged to someone else now, she’s moved on. Also, she’s been seen leaving with Jack at the end
Donna: All the clues are pointing to Donna, she’s been told she’ll die, she goes on about being a temp, she’s not in the next series, little things. And then there was that comment about her loss which is yet to come… Suggestions are that she may die, but be brought back with total memory loss.
Sarah Jane Smith: She’s been faithful to the Doctor for years. Even when he abandoned her she still came back, but she has her own series to look after, and Elisabeth Sladen has said that she doesn’t think she’ll be coming back. So it’s not as certain as it would be if she actually died.
The TARDIS: Is there a companion more faithful than his ship and the living being at the heart of it? Captain Jack is growing a TARDIS on his desk back at Torchwood, which would give them a way to continue with Dr Who.

Regeneration: At the end of the episode came the massive cliff-hanger regeneration and the “To be continued.” Is it real?

He may regenerate into himself. The had in a jar may be significant and allow him to draw on his own DNA to keep his appearance. He doesn’t appear to think this though, as he apologises to Rose for regenerating, suggesting that he expects a change.
He may reverse regenerate into a previous incarnation, Christopher Ecclestone and Sylvester McCoy have both been mentioned as possibilities
He may regenerate properly. A number of names have been bandied about, and most of them have said that they haven’t heard anything regarding the rumours and that they haven’t been approached. Maybe someone’s lying or the true regeneration hasn’t been mentioned
We might get a botched regeneration into the Valeyard, which would be really really bad news
A regeneration which doesn’t change him but creates a second Doctor with only one heart, a human Doctor who will probably die or leave to live with Rose

Other theories I like:

Is Donna a Time Lady? Suggestions that she may have a fob-watch concealed about her person are popular, especially considering her name and her job. Noble who is a temp. Classy
Mickey the Idiot and Jackie Tyler turn up in the nick of time to save Torchwood and Sarah Jane Smith. Someone has to. SJS has to survive for her series and Ianto and Gwen can’t die outside their own, can they? Someone will not be happy is Ianto dies.