Who is Richard Mesington from The Rifle and what is their importance?

Richard, in 1993, is a fourteen-year-old typical American boy. He was born in Colorado, and spent several years of his boyhood in a town named Willow. His constant companion during this time is a border collie named Sissy, who is initially jealous of the attention Richard's parents spend on the boy, but who eventually comes to love the boy dearly and follow him around constantly.