Hey look! A Dungeons and Dragons ride! That's how it all started. A simple ride on a fun fair. The next thing they knew, Sheila, Bobby, Hank, Diana, Eric and Presto get transported into a magical land, where they are guided by Dungeon Master.
The meet the evil Vengar, and Tiamat the dragon, and the point to the series was to try to escape back out of the land.
In one episode, they did actually manage to get back onto normal earth, but the problem was that so did Vengar. So they decided the only way the earth could be safe was if they lured him back in by going back in themselves.
Cartoons with morals. Those were the days.
Incidentally, Eric the Cavalier was voiced by Donny Most - Ralph from Happy Days.