Inside Man: Double Threat by F. Paul Wilson
In F. Paul Wilson’s Double Threat, the main character, Stanka Daley, is a con artist who makes the fateful, life-changing decision to hide out in a desert cave while on the run from some angry housewives she scammed with a fake car contest.
While Daley, as she prefers to be known, hides in that cave, a strange slug-like creature drops on her head and knocks her out. When she comes to, she stumbles to the house of Juana, a local who watches over the cave and who informs her that surviving an interaction with the alaret, as the creature is known, is a vanishingly rare occurrence, and that she will now serve as Daley’s guide.
Daley isn’t sure what to think when Juana tells her that her life will change forever, but she soon finds out what she means when she starts seeing a man following her and hears his voice in her head. Is she going insane, or did something far stranger happen to her because of the alaret?