What is the main conflict in Dead Sleep by Greg Iles?

DEAD SLEEP is a mystery thriller that follows photojournalist Jordan Glass as she investigates the disappearance of her twin sister, Jane, who she believes is the victim of a serial kidnapper and possible serial murderer. Working alongside the FBI, Glass is able to identify the murderer and narrowly escapes becoming a victim herself. As she unravels the mystery she not only learns that her sister is alive, but also discovers the truth about the apparent disappearance of her father several years before.