One day, a man pulled over and parked the orange Porsche he was driving away from the lot, on Chestnut Street between our house and the Lees', who lived next door to us on the other side. I was playing alone in the front yard; I noticed an inordinate (a word I did not yet know) amount of smoke blowing from the car's exhaust pipes (a term with which I was familiar at the time). Because of my experience watching my parents dealing with their Volkswagens, I took it upon myself to inform him of the problem (it might have been a blown gasket or some other oil leak).
The man was reading a map; he abruptly dismissed me and my observation ("Oh, that's alright; it's normal...), then went back to studying his map. I was not satisfied; something was not right. I walked back behind the car and assessed the situation. The tailpipes (another familiar term) weren't smoking as much as they had just been, but now there was some liquid dripping from them.
I returned to the driver's window, got his attention, and informed him of the latest development. He dismissed me again, saying something like, "Don't worry about it, kid." I was still concerned; I had never seen a car do what this one was doing. I went back to the rear of the car; there was fire coming out of the exhaust pipes!
I went and informed the man about the fire; he was not amused, but he decided to humor me ("Oh, come on, kid..."). He got out, walked to the back of the car and gasped when he saw the flames shooting out of the tailpipes. Within a few seconds, the car was completely engulfed in flames.
I remember watching that Porsche burn; the paint bubbled on the body of the car, and the tires melted onto the road. The Bethesda-Chevy Chase fire department arrived minutes later, hooked up to the fire hydrant in front of our house and extinguished the blaze. I remember the man picking me up and pretending to throw me onto the fire; I cannot remember if he thanked me for saving his life.
Afterward, there was a black spot on the road where the car had burned; it stood for years (it was still there when we moved away four years later) as a reminder to me of the difference I could make by persistently not minding my own business.