Hari Seldon's plan is rumored to have secretly involved not only the scientificly minded foundation to preserve knowledge and steer humanity into a better and brighter future, but also a Second Foundation, one where the people are rumored to have magic powers. The people from the first foundation want to find the Second Foundation, because they think their own plans are endangered by their existence.
The whole Foundation Series is simply awesome. 7 books in total, they are all worth it. And all the rest of Asimov is worth it too.
Foundation Novels in Order:
- Foundation and Empire
- Second Foundation (this book)
- Foundation's Edge
- Foundation and Earth