U is for Undertow — Sue Grafton

Looking solemn, Michael Sutton arrives in Kinsey Millhone's office with a story to tell. When he was six, he says, he wandered into the woods and saw two men digging a hole. They claimed they were pirates, looking for buried treasure. Now, all these years later, the long-forgotten events have come back to him -- and he has pieced them together with news reports from the time, becoming convinced that he witnessed the burial of a kidnapped child.

Kinsey has nearly nothing to go on. Sutton doesn't even know where he was that day -- and, she soon discovers, he has a history of what might generously be called an active imagination. Despite her doubts, Kinsey sets out to track down the so-called burial site. And what's found there pulls her into a hidden current of deceit stretching back more than twenty years ...