U is for Undertow (Kinsey Millhone Mysteries)

It's April, 1988, a month before Kinsey Millhone's thirty-eighth birthday, and she's alone in her office doing paperwork when a young man arrives unannounced. He has a preppy air about him and looks as if he'd be carded if he tried to buy booze, but Michael Sutton is twenty-seven, an unemployed college dropout. Twenty-one years earlier, a four-year-old girl disappeared. A recent reference to her kidnapping has triggered a flood of memories. Sutton now believes he stumbled on her lonely burial when he was six years old.