Tonight's ride home I decided to stop at the bank and take a longer route home. After stopping at the bank and heading on home, on a rural road my pedals stopped turning. I got off the bike looked at it quickly and could not figure out what was wrong. I started walking my bike home the seven miles I had left, that lasted at best two minutes. I was going to call a taxi, when I realized I had the bike shops phone number in my cellphone from last nights flat tire incident. I called the bike shop explained what happened. He told me what he thought it was, and he was right, the chain was off the rear cog at the very small end. He told me how to put it back on and that my hands would get dirty. I hung up the phone and put the chain back on, then finished my ride home. So all in all a very good learning experience for me. I have never had the chain come off of my bike before.