Anna Milton is a young woman being held in a psychiatric institution called the Connor Beverly Behavioural Medine Center because she has been trying to warn people of the upcoming apocalypse and she can hear voices in her head which are the voices of angels. She has the knowledge about the upcoming apocalypse and knows that Lilith is trying to break the 66 Seals and release Lucifer, so all hell can break loose on Earth. When a demon tries to kill her she manages to escape with the help of some form of psychic power in the process. Anna takes refuge in a church where her father was once deacon and thanks to the demon Ruby, Sam and Dean Winchester track her down after finding her parents dead. She recognises both brothers , since she has heard the angels talking about Dean , as the one who may save them. She reveals that some of the angels don't like Sam. The demon Alistair appears and is immune to Sam's powers and beats Dean up. Dean recognises him from encountering him in Hell. In the chaos, Ruby takes Anna to safety even though she is scared because she can see Ruby's demon face. Eventually she meets up with the Winchesters brothers, and than the angels Castiel and Uriel appear to take her away and dispose of her.
Now Anna Milton is on the run, with Sam and Dean and Ruby from the demons who want her and the angels that want her dead. It is later revealed that Anna is an angel who chose to fall to Earth and become human, relinquinshing her grace. During an fight againest Alastair, she gets her Grace from Uriel and becomes an angel once more, sacrificing herself to save everyone else. As Dean is torturing Alastair, Anna appears and challenges Castiel about what he is doing, and why he thinks God would order torture. She encourages him to rebel, and join he rejects the offer. Later as his doubts grow, he calls on Anna and asks her for guidance, but she says he must choose his own choice of action. After Uriel's treachery is revealed, and Castiel refuses to 'convert', Uriel attacks Castiel, and he is saved by Anna killing Uriel with the Sword of Lucifer. Anna visits Dean and Sam and tells them that Castiel was sent back to Heaven, and that Castiel knows something important that Jimmy Novak may know, and encourages them to find him. Anna visits Castiel, and confronts him over his actions in releasing Sam, but he says he is acting on orders, and she is taken captive by other angels.
Anna appears in a dream to Dean. She tells him she has been held prisoner and tortured in heaven, after Castiel turned her in. Because of the Enochian Sigils on his ribs, she can't find Dean and asks him to meet her. Castiel arrives instead, and charges that she has been sent on a mission from heaven, which she denies, insisting she is following her own agenda. Anna says she intends to kill Sam to prevent Lucifer taking him as his Vessel. Castiel says he is willing to kill Anna to protect Sam. Anna travels back to 1978 intending to kill Sam's parents and prevent his birth. When Castiel sends Sam and Dean there as well, she enlists the help of a younger Uriel to kill them. However Michael arrives, killing Anna and sending Uriel back to Heaven.
