Who is Arthur Ownby and what is he doing as this chapter begins?

Arthur Ownby--the real name, as it turns out, of the man referred to so far as "Uncle Ather," "the orchard keeper," or simply "the old man"--is traveling outside in a severe downpour of rain. Despite his old age, he seems to manage the wet terrain dexterously at first, hopping from one firm spot to another, but eventually he slips and lands bodily into the wet mud.