She is the neighbor and girlfriend of Henry James, the son of the story's protagonist. She becomes pregnant with Henry's child and is sent to a Catholic school by her father because of this. After Henry breaks her out of the school, the two start a Bonnie and Clyde style crime spree, calling themselves "the Sweetheart Bandits" and make national headlines. Shannon is shot in the back during a robbery and goes into labor as Henry tries to drive her to safety. She eventually dies in his arms after the pair takes shelter in a warehouse.
"The baby is dead, and I want to die, too. I can’t stand the pain. It’s terrible. I love you, honey, but put me on the ground."