Where There's A Will, by Aaron Elkins

Gideon goes to Hawaii to visit with his FBI friend, John, who grew up there. They are scheduled to stay at the ranch where John worked as a teenager, which was founded and run in the 50s by three Swedish former sailors and their sister.

The sister is the only one of that generation still living, but just as John and Gideon arrive, news reaches them that the airplane one of the brothers was last seen in has been discovered in a lagoon across the Pacific.

The family asks Gideon to go with John and recover any remains there may be, although after 10 years everyone is doubtful there will be anything left by the fishes.

Of course there is just enough evidence to make life miserable for everyone from the family members to John to the local police force. There are also a lot of confusing twists and turns. Luckily, Gideon never ends up in physical danger (for a change). I pretty much knew who the "bad guy" was from the git-go, but this was a fun book to read anyway, just to try to figure out WHAT was going on!!