J.R.R.Tolkien has confessed that about a third of the way through The Fellowship of the Ring, some ruffian named Strider confronted the hobbits in an inn, and Tolkien was in despair. He didn't know who Strider was, where the book was going, or what to write next. Strider turns out to be no lesser person than Aragorn, the unrecognized and uncrowned king of all the forces of good, whose restoration to rule is, along with the destruction of the evil ring, the engine that moves the plot of the whole massive trilogy, The Lord of the Rings.
Ansen Dibell (1988). “Plot”, Writers Digest Books