Shadrack returns from WWI suffering from shell shock or, as it's known today, post-traumatic stress disorder. Upon his return to the Bottom, he institutes National Suicide Day in an attempt to gain some control over death. It doesn't catch on, but people eventually stop fearing him.
Years later, Shadrack meets Sula. Her visit to his house becomes a happy memory for him, and he clings to it throughout his life.
Shadrack disappears for much of the novel, but he reemerges near the end after an especially difficult winter. Although he's not as enthusiastic about the ritual of National Suicide Day this year, a sense of duty compels him to march anyway. For the first time, most of the townspeople join him on his trek, following him to the unfinished tunnel as if he were the Pied Piper. Most of them die when the tunnel collapses, but Shadrack survives.
Our final image of Shadrack is when he passes Nel on the street as she's leaving the cemetery. He's thinking about how there are no more fish to catch. While he recognizes Nel for a split second, he continues to walk past her, lost in his thoughts.