Summerlin Groves by Elizabeth Camden

Jenny Summerlin is struggling to save her dying orange grove when a baffling mystery upends her world. A skeleton buried with a priceless treasure has been found on her land, which brings of flood of investigators onto her property to study a decades old crime.
Captain Wyatt Rossiter is charged with solving the puzzling discovery. Unfortunately, he is also the man who broke Jenny’s heart two years earlier. Plagued with regrets and unresolved feelings for Jenny, Wyatt resists getting drawn back into her world, but he cannot rest until he solves the unusual crime.

The former lovers are trapped on a case neither of them want. Soon they awaken a fifty-year old mystery involving Cold War espionage and a forbidden romance. Will resurrecting the old secrets endanger the survival of her grove and everything she holds dear?