on the run
The extreme nit-picking will be saved for later sections as this is more of an overview of Anna's storyline as it weaved in and out of Sam and Dean's. This isn't intended to be all that in-depth because a) I want everyone to go out and watch the show, and b) writing detailed episode summaries is not fun for me. I do, however, feel it's important to provide a bit of a context for those who haven't seen the show or perhaps just can't remember, so here you are!
I Know What You Did Last Summer
Later, Anna was alone in her room drawing when an orderly came by to give her medication. When she turned from look at him she was absolutely terrified and demanded to know what had happened to his face. As a matter of explanation the orderly's eyes turned black, revealing that he was possessed. Before he could get to her, through some unknown power Anna telekinetically flung a dresser at him, knocking him unconscious, and then fled the room.
Sam and Dean, following a tip from Ruby, went to find the missing Anna who for reasons unknown seemed to be both Heaven and Hell's most wanted. When they visited the hospital where she had been they were surprised to see that the pictures in her sketchbook depicted recent incidents surrounding the breaking of the seals. They continued their investigation at her house, where they found no sign of Anna but both her parents dead on the floor - sulphur nearby indicating demons were involved in their deaths.
Their next stop was Anna's church, with the reasoning that Anna was religious and it was the logical place to hid when on the run from demons. And there she was, but what neither brother expected was that she was actually excited to meet Sam and the Dean. It seems that Anna was able to hear the voices of angels ever since the day Dean was pulled out of Hell, and felt like she knew the Winchesters already from all she had heard said about them.
But the meeting was cut short by Ruby bursting into the room with a badass of a demon on her tail. Too late to escape, Sam and Dean fought uselessly against the demon while Ruby grabbed Anna and ran, resulting in the two groups being separated.
Sam and Dean holed up in a motel room, waiting for a sign from Ruby, and she lived up to Sam's expectations by sneaking into their room in the body of a housekeeper to tell them where she and Anna were hiding - a lovely little cabin in the middle of nowhere. They arrived to find Anna safe and sound, but the Hallmark moment didn't last... First there was the awful business of breaking the news of her parents' death, and then Anna wasn't even allowed time to properly mourn as right after Sam told her the lights start to flicker and all Anna could say was "They're coming." Sam quickly hid Anna in the back room, and moments later Castiel and Uriel burst through the door and demand they hand Anna over - because she had to die. (Dun dun dunnn)
Heaven And Hell
Understandably worried and unsure of what to do, Sam, Dean, and Ruby took Anna to Bobby's panic room where she would be safe. Unable to find any conclusive answers by digging into her records - and pissing off Anna in the process by not asking her directly - the best solution seemed to be bringing in Pamela to try and find the source of Anna's abilities in her subconscious. Putting Anna under hypnosis didn't seem to be working until Pamela asked about her real dad and why he was angry; Anna lost it, lights exploded, and it was all in all rather eerie.
Even more eerie was the stark contrast when Anna came out of the trance and suddenly was well beyond calm. But the change made perfect sense when Anna explained what was going on: she was actually a fallen angel. And because of that Hell wanted to get a hold of her for information on the angels and Heaven wanted her dead as she was both a criminal and a liability. The last thing Anna wanted was to return to the life she had escaped from all those years ago, but with everyone after her the only choice she had was to find her grace - her angel mojo which she had ripped out when she fell - and turn back into a full-fledged angel. And Sam and Dean, being Sam and Dean, agreed to help. Even Ruby stuck around, if only for Sam's sake.
They tracked Anna's missing grace to somewhere in Kentucky, but when they got there it was clear that although her grace had been there, someone had beat them to the draw. Their only plan a failure, our intrepid heroes were forced to hole up in a barn to try and think of what to do next. While Sam, Dean, and Ruby were arguing the other angels sent them all a message via Anna - if they didn't hand her over by midnight Dean would be sent back to Hell.
Dean didn't want to give up but Anna was starting to think otherwise. Later, when he was alone outside the barn Anna approached him to thank him for his help, but she was starting to doubt whether she really deserved to be saved. Dean felt he knew about doing something unforgivable, and that gave Anna the chance to bring up the fact that she had overhead the other angels talking about what Dean had done in hell. Dean wasn't even close to wanting to talk about it, but she wanted him to know it was ok and that he had people there for him when he was ready.
And then she kissed him. And played Dean's personal favourite: the "last night on Earth" card. Cue steamy sex scene in the back of the Impala!
Afterwards while Dean was sleeping, Uriel approached him in his dream and revealed that he had Anna's grace, kept safe in a small vial around his neck. Uriel also told Dean if he didn't give them Anna they would kill Sam. Forced to choose between the two, of course Dean had to go with Sam. While that was happening, back at the barn Ruby slipped off to meet up with Alastair and offered to hand over Anna if she and the Winchesters could go off scott free.
Except it was all a sneaky plan, and then next day when Uriel and Castiel came for Anna, Alastair wasn't far behind. This left Sam, Dean, Ruby, and Anna to stand back and watch the opposing teams fight it out. It was during the resulting chaos that Anna spotted her grace hanging from a vial around Uriel's neck and snatched it while he was distracted fighting an underling. Before anyone could stop her she smashed it against the ground and she overflowed with power as her grace flowed back into her. Just as looked like the demons might have the edge, Anna exploded in a brilliant flash of light, and when the smoke cleared both she and the demons were gone. That was the end of human Anna.
On The Head Of A Pin
Anna asked Castiel why they were having Dean torture Alastair and questioned whether or not it truly was God's will. Castiel appeared to be listening to her, but the minute she tried to tell Castiel that he was experiencing "doubt" and asked him to join her he grew angry with her and told her to leave. Looking quite heartbroken, Anna complied.
But then everything went wrong; Alastair broke free of his bonds and nearly killed Dean before being stopped by Sam who arrived in the nick of time. Finally, Castiel started to question what was going on and if God really was the one calling the shots. When night fell he stood alone and called out to Anna - the only person he could turn to - and to her credit she appeared and asked him what he wanted. His response was too wonderful to not quote directly: "I'm considering disobedience." Anna saw it as a good thing, but Castiel didn't agree. He still had his doubts about doubt, and when Anna reached out for him he turned away, which Anna saw as a sign of his thinking she was still "a walking blasphemy." As she turned to walk away he tried to get her to tell him what to do, but she told him he had to think for himself and left.
And then Castiel had a revelation. When he saw a nearby faucet he realized how Alastair had broken free and went back to where it had happened and found a leaky pipe that had worn away at the devil's trap he had painstakingly drawn on the floor. Castiel called Uriel to the scene and confronted him, but never could have expected what came next; Uriel had been the one killing the angels. He was trying to get all the members of their garrison to join him in supporting Lucifer, and killing all those who refused.
Uriel asked Castiel to join him, but Castiel naturally refused and things came to blows. Except Uriel was stronger and Castiel was very much getting his ass kicked. Still Castiel refused to side with Uriel and stated quite devoutly that he served God. Uriel, standing over him, told him that there was no God, but at that moment Anna appeared behind Uriel, drove his own blade through his throat, and told him quite viciously that there was still her. She then stood by Castiel's side and watched as Uriel died in a burst of light. Perhaps Anna's single most badass moment of season four? But after that the two angels parted ways and Castiel finished off the episode on his own.
It was at this point that she noticed something different about Sam, which he shrugged off as a new haircut, but we the viewers know he'd been consuming demon blood to grow stronger. The fact that an angel could actually sense it was a big sign that he'd gotten himself in way too deep, but that's a storyline that Anna never really got to be a part. That's probably because Anna was there to ask after Castiel, and when Dean told her Castiel had wanted to tell him something but they never found out what that was, even from Jimmy, she grew even angrier and told them off more for losing him.
She didn't team up with Sam and Dean to help them find him, however, which is not to say that she wasn't helping, but that she was going solo. That just seems to be how she rolls.
When The Levee Breaks
The Song Remains The Same
It didn't take long for Castiel to figure out what Anna was up to. He took Sam and Dean back to 1978 to stop her, but the effort of doing so put him right out of commission, leaving the boys on their own. They went straight to their parents' house and used Dean's previous encounter with Mary in the past as leverage to pretend to be her relatives from out of town. However, while they were giving her an explanation filled with half-truths, Anna lured John away from the house by calling and pretending to be his boss - who she had actually killed. Things would have been grim for their father-to-be, but the cavalry arrived just in time and Mary and Anna battled it out in a fight scene that was nothing short of badass. This of course gave Sam time to draw a blood sigil to cast Anna away, then the four of them fled to an old safe-house that belonged to Mary's family.
But Anna was smarter than the average terminator and knowing she was outnumbered summoned a younger Uriel to aid her. When he questioned why she was on Earth despite orders to stay away, she claimed that she had come from the future to destroy some humans who would eventually kill him (oh Anna, such lies!). The two attacked all four Winchesters in full force and things were going very poorly for our intrepid heroes. John was tossed from the house and Anna actually managed to kill Sam with a piece of rebar, but just as she was about to kill Mary John returned, all full up of Michael. It seems that being his vessel has to do with bloodlines and it was something Dean had inherited. With one touch Michael burnt Anna to a crisp - nothing was left of her but a pile of ash.
Michael erased John and Mary's memories of the whole ordeal and sent Sam, Dean, and Castiel back to the future. And for all we know that was the last we'll ever see of Anna...