The secret of how to turn poison into beer, for one thing. Well, she was shown how, but she learned something more about the trick than people knew before. But there was something more important than that.

What was it?

She was the one who realized that the island she'd washed up on had a history more brilliant and amazing than anyone had realized for hundreds and hundreds of years.

Why didn't they know?

The place their knowledge was kept had been hidden.