I have two possible ideas.
One is set in the Constantine Verse, it could go similar to the movie, or it could be an original story that we could come up with.
The other idea is that perhaps theres a war going on between heaven and hell. I could be one fighting on the side of heaven, and during battle, I'm injured somehow and use my powers to try to escape the battlefield, only instead of appearing where im supposed to be, I appear on Earth, somewhere in the US, in a hospital,having appeared from nowhere in an alleyway,or somewhere else, and was admitted to a hospital.
I could have amnesia,or perhaps not. My powers would be muted on Earth, but i would still have them. Someone playing against me in this would be someone taking me in, giving me sanctuary, with no idea of who or what I am, or perhaps they do.
if it appeals to anyone, please let me know.