Hey, looking for a story I read years ago on fanfiction where Dean is abducted by aliens. (NOT SEASON 6)
I'm pretty sure it was set in either season 1 or 2 and the brothers are working a case about people getting abducted. I remember a certain amount are abducted by aliens and I think its the last one who they return.
The brothers go to the place where the last abduction took place, even though I don't think they believe its aliens. When the spaceship turns up Sam tells Dean its here and Dean's like 'really? I hadn't noticed'. Dean gets abducted and Sam goes back to see someone who had previously been taken & they tell Sam that Dean will return on a certain day in the place where he was taken and when Sam goes back to that place he finds Dean who is traumatised. I'm sure the aliens have tentacles or something and abuse Dean, and they continue to traumatise him even when he's asleep and safe with Sam.
I'm also sure John turns up at some point and tries to help his son.

Hopefully someone recognizes it, would love to read it again.