In the first five books of the Foundation Series, Hari Seldon made only one in-the-flesh appearance, in the first chapter of the first book (Foundation), although he did appear other times in pre-recorded messages in order to reveal a Seldon Crisis. After writing five books in chronological order, Asimov went back with two books to better describe the initial process. The two prequels—Prelude to Foundation and Forward the Foundation— describe his life in considerable detail. He is also the central character of the Second Foundation Trilogy written after Asimov's death (Foundation's Fear by Gregory Benford, Foundation and Chaos by Greg Bear, and Foundation's Triumph by David Brin), which are set between Asimov's two prequels.