He blows out a tire. When he gets out of the car, he happens to notice a sign saying "Homewood, 2 miles." Homewood! That's where he grew up. Leaving his car at a service station, he walks into town. His first stop is the soda shop where, incredibly, it looks exactly the same as when he was a kid --- and he can still get a chocolate soda for a dime. As he's enjoying the treat, a woman Martin knew as a kid comes in. She is unchanged. In fact, Homewood itself is unchanged because somehow Martin has wandered back in time, where he makes the most unnerving acquaintance of all.
We learn in the afterword that Rod Serling, author of the original stories, considered this to be his most personal Twilight Zone episode, which was based on memories of growing up in his own hometown. This might explain why it is so affecting, tugging at readers' heartstrings and giving them much to ponder in a quick-reading, enjoyable format.