The world is veiled in darkness. Winds don't blow, the seas are stormy, and the earth rots. All people can hope for is that the ancient prophecy will be finally fulfilled. "When the world is veiled in darkness, four warriors will come..." And indeed, they come - the four characters you have previously chosen. Their first quest is to free a princess from the evil knight Garland, and then the real journey begins.
...or that was the intention, anyway. Instead, the heroes walk up and down some stairs, talk to a random person in the castle, and the final boss conveniently shows up.
You can watch the complete run played back on console.