The other night I was driving and suddenly my car died. It had been running for about 20 minutes, and it has been very cold here for several months. The engine stopped and all of the lights went off. When I tried to start it, the lights came back on but there wasn't enough juice to turn the engine over. I tried jumping it, it turned over, but wouldn't fire. I called a tow truck and we tried jumping it again. Eventually it started, but as soon as the cables were removed it died again. Jumped it again and it wouldn't fire. Tow truck driver suggested my battery was history. When he removed the cables, I noticed that the small wire that was attached to the positive battery terminal had become disconected. I dont know if it had been disconected before the jumping, or if it happened during. I've never had one die before where all of the lights went off, so that kind of worries me. Also, it seems like it's an electrical thing or possibly a fuel thing (or both). The fuel pumps are about 4 years old, as is the battery. The car is an '86 with about 240K miles.

So my questions are:
1- What would make it die and take all of the lights go with it?

2- What is that wire that is attached to the positive battery lead?

3- Other than the battery and the battery terminals, what should I check next?

Thanks for any ideas as to the cause and repair!

John