This episode is much cleverer than I first gave it credit for. It initally seems to be a run-of-the-mill yarn, with that cliche of a character unaware he has died, but evolved into something much better than that.
A young woman and her dog are nearly hurt in a car accident, after which they see a bus full of scary looking people. The bus continues to haunt the engaged English teacher. Her memory begins to alter, and total strangers seem to know her. The climax to the story is great, so I don't want to spoil it, but I'll say that it wraps up all the elements in the story, and shows that the womans perfect life has in a way, passed her by like the bus.
With interesting symbolism, and the classic 'i'm-seeing-things-no-one-else-can' plot of many twilight zone episode, this is a real treat of an episode.