This episode has a "twist" ending, if there ever was such a thing. I'm amazed by all the negative reviews here. This was a truly suspenseful, thoroughly enjoyable episode. Robert H Harris made at least two previous appearances in the series. This was his best performance, up to that point. He had me convinced that he was a "professor," until it was confirmed that he was only a "nut"! Biff McGuire was also good as the young man trying to remember the license plate number. I do think that the ending is a bit disappointing, because the identity of the driver is not revealed. However, the look on Harris' face, when the inspector called him a "nut," was priceless. I was laughing for about 10 minutes. The people who criticized this episode obviously don't know good storytelling when they see it. Sometimes, a TV show can require you to actually use your brain.