It's of John picking Sam and Dean up from school to move on to the next town.
The episode talked about Sam wanting to get out of the hunting life and do something different and yet he was back at the school working a case as a hunter. I was really struck by the creepy shadows of the trees. They look like hands reaching out to grab Sam. The fact that the grabby hands appear to be coming from the car seems significant too with the car being so much a symbol of the Winchesters and hunting. Then there are all the dead fall leaves. He's surrounded by death and has been since he was 6 months old. The shot is from the window from the perspective of a friend of Sam's being left behind. It seems to me that a lot of people have had this view of Sam. In season 5, Bobby makes a comment about how Sam has been running into burning buildings since he was 12. He's been walking away or been dragged from the life he's wanted for a lot longer than that.
Cap from Home of the Nutty.