Palettes, Patriots, and Prats - Esther Brookstone Art Detective, #4

Esther Brookstone, ex-Scotland Yard inspector in the Art and Antiques Division and ex-MI6 spy during the Cold War, and new husband, Bastiann van Coevorden, have just returned from their honeymoon cruise down the Danube, refreshed and reinvigorated despite Bastiann's having to handle a murder investigation as his last assignment as an Interpol agent. Esther is content running her gallery, and Bastiann works as a consultant for MI5.
They hope to enjoy their active golden years together, but more adventures as sleuths await them, colliding with their idyllic existence, as they aid an American artist, try to thwart a Russian assassin, and go after the illegal art trade and human traffickers.