For a few months in the late 1970s, Larry, the child of lower-middle-class white parents, and Silas, the son of a poor, single black mother, stepped outside their circumstances to become pals. Then tragedy struck: Larry took a girl on a date, and she was never heard from again. Larry never confessed, but all eyes rested on him. The incident broke their friendship, and then Silas left town. Twenty years later Larry, a solitary mechanic, and Silas,...