Series numeration from GoodReads.

"A Stone Barrington novel" -- from front cover.

"Stone Barrington and his friends are vacationing in Maine when their leisure is suddenly disrupted by extreme weather. To make matters worse, the inclement conditions allow for a menacing adversary to sneak in unnoticed and deliver a chilling message. Soon it becomes clear that the target of the incident is one of Stone's closest companions, and that these enemies have a grander scheme in mind. From the bustling streets of New York City to the sun-drenched shores of Key West, Stone intends to nab the criminals that appear behind him at every step. But his search only leads him further down a trail of peril and corruption, and he'll soon find that at the end of the road is a more dangerous foe than he could have imagined...." from book jacket.