U is for Undertow (Kinsey Millhone, #21)

It's April 1988, a month before Kinsey Millhone's thirty-eighth birthday, and she's alone in her office catching up on 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 a beer, but Michael Sutton is twenty-seven, an unemployed college dropout.
He tells her a story. More than two decades ago, a four-year-old girl disappeared, and a recent newspaper story about her kidnapping has triggered a flood of memories. Sutton now believes he stumbled on her secret burial and could identify the killers if he saw them again. He wants Kinsey's help in locating the grave and finding the men. It's way more than a long shot, but he's persistent and willing to pay cash up front. Reluctantly, Kinsey agrees to give him one day of her time.
It isn't long before she discovers Sutton has an uneasy relationship with the truth. In essence, he's the boy who cried wolf. Is his story true, or simply one more in a long line of fabrications?
Moving between the 1980s and the 1960s, and changing points of view as Kinsey pursues witnesses whose accounts often clash, Sue Grafton builds multiple subplots and memorable characters. Gradually we see how everything connects. And as always, at the heart of her fiction is Kinsey Millhone, a sharp-tongued, observant loner who never forgets that under the thin veneer of civility is often the roiling dark side of the soul.