What is the importance of Fishers Island, New York in the novel, The Terminal List?

Fishers Island, New York is one of the more important settings because it is the site of the showdown between Reece and Ben. This takes place in an elegant home rented by the Hartleys, supposedly as a planning location for their foundation. The estate is beautiful and near the ocean. Reece arrives by boat. Reece kills Ben, Lorraine, and Horn here, along with five men who were supposed to be providing protection.