Fatal Finale by Nancy Mehl

When bestselling author Erin Delaney's novel gets picked up for a movie deal, she eagerly awaits her friend Kaely Quinn-Hunter's arrival in Tennessee before they head to California to observe the film's production. However, when Kaely does not arrive at the scheduled time and Erin can't reach her by phone, her concern grows.

A cryptic phone call from Kaely's kidnapper confirms Erin's worst fear--she has exactly six days to save her friend's life by solving his twisted clues. The message comes with a warning: Contact the police or FBI, and Kaely dies. But Erin works for the Sanctuary Police Department, and Kaely's husband is with the FBI, putting her in an impossible situation. As Erin races against time, she's forced to crack the kidnapper's chilling puzzle before it's too late.