1991 Other Oldsmobile Models Car gets no electricity

I walked out to my car the other day and it was dead. My friend tried to jump it and initially I was getting some juice but not enough to turn it over and then I couldn't get anything- no lights, radio etc. The jumper connection was checked and rechecked and I'm sure that isn't the problem. I briefly looked at a couple of the Maxifuse/Relay center fuses and I they seemed fine. What could cause the whole electrical system to stop working?