The Other Side of Silence by Bill Pronzini

The story features Rick Fallon, a newly divorced man, who goes to Death Valley as a way to clear his head.  He loves the desert for the quiet, solitude, and stark beauty.  On his fourth day there he finds an abandoned car and soon finds the nearly dead Casey Dunbar.  After rescuing her, Fallon learns why she had come to Death Valley to die.  Casey tells him that her ex-husband has taken their 8-year-old son and sent someone to assault her and threaten her with more if she tried to find him and their son.  She asks for Fallon's help in getting her son back.  Pronzini writes believable characters.  I felt like I knew Rick Fallon and rooted for him as he tried to help this woman and deal with the problems in his own life.