Debbie Does the Desert by Dean Wesley Smith

Sky Tate, the best female detective in the world, gets a new client by the name of Debbie. Debbie seems, at first glance, to be desperately trying to find her boyfriend. But first glances can often be wrong, and in this case, very wrong. Sky calls in help, including Marble Grant and her partner, Sims, two ghost agents. As it turns out, the bottom of Debbie’s problems run far deeper than an old boyfriend.