U is for Undertow by Sue Grafton

U is for Undertow - Its 1988, Michael Sutton comes to Kinsey Millhone’s office with a memory that might solve a kidnapping that happened over 20 years before. However, Sutton’s sister, also comes and informs Kinsey that Michael doesn’t tell the truth. Back in the 60’s, the Unruh’s are living out a family drama. The son, Greg, has hooked up with Shelly, who has an undisciplined son. The couple is doing their best to get the elder Unruh’s to support them.