'Switcheroo' by Aaron Elkins. Somehow I missed this 2016 (and currently last) entry in the series. I've been a fan since the 2nd entry ('The Dark Place'). This is about the weakest entry of the series; perhaps why he hasn't written more. If you know the old tv series named after the main character (Gideon Oliver), it has little to do with the books other than the name of the title character.