Searching for Stardust by Lorena McCourtney
Jan Hilliard is on a lonely forest trail in an isolated corner of Oregon for one reason only, to learn the truth about her son's death. The last person she expects, or wants, to encounter is the ex-husband whose fierce ambition and betrayal destroyed their marriage.
Jan wants nothing to do with Mark. Even as she realizes he's still interested in her, and, worse, feels an unwanted attraction for him, she's skeptical both of him and his new Christian faith. But she knows she needs his help to learn the truth about their son and reluctantly joins forces with him.
And then the mysterious Stardust emerges from their dead son's journal. Who is she? What does she know about his death? Where is she? Is she even real, or is she as imaginary as the monsters in the journal?