The second Katie Maguire novel.
Barnes & Noble.com
After recovering from her nearly fatal exposure to a terrorist's deadly virus (read A Necessary End), Officer Katie Maguire and her best friend, Officer Marty Goldman, are rewarded for helping to save the world from a global pandemic with a one week Caribbean cruise aboard the MS Atlantis Pearl. The trip is going well until the ship docks in Kingston, Jamaica, where things quickly take a turn for the worse. Their problems start when Katie and Marty decide to go on a horseback riding excursion into the mysterious Blue Mountains located in the eastern tip of the large tropical island. Formerly a haven for pirates, it is said that the mountains and adjacent castle ruins along the coastline still harbor the ghosts of these long-dead buccaneers. The two Miami cops, along with their superstitious Jamaican trail guide and seven other members of the tour group, must soon deal with one disaster after another along the isolated horse trail. And then they discover they are not alone.