Dead heat
(Book)

"For once, mated werewolves Charles and Anna are not traveling because of Charles's role as his father's enforcer. This time, their trip to Arizona is purely personal-or at least it starts out that way... Charles and Anna soon discover that a dangerous Fae being is on the loose, replacing human children with simulacrums. The Fae's cold war with humanity is about to heat up--and Charles and Anna are in the cross fire" --,from publisher's web site.