Skoda Felicia lights dimming

I was driving along the motorway, when all of a sudden, all the lights in the car dimmed, the windscreen wipers slowed down, the radio started to crackle and the seat belt light came on....

eventually the car stalled (thankfully I was off the motorway), the oil light and seat belt light were still on but very dim and the head lights were barely noticeable. I tried starting the car straight away, but it was completely dead.

I stayed in the car for awhile and decided I would have to walk the rest of the way home. I thought I'd try to start it one more time and it started...lights bright as ever, drove home without hitch. Switched off and on again and it was fine. Can anyone tell me what happened? (I think the alternator might be on the way out! - that's all I know)
Thanks!