The Web (Alex Delaware, #10)

Dr. Woodrew Moreland, a respected scientist, has invited Alex Delaware, psychologist/detective, to his home on a tiny Pacific island to help him organize his papers for publication. It's a light workload leaving plenty of time for Alex and his girlfriend, Robin, to relax.
Quickly, however, secretive houseguests and unexplained visitors dim the pleasures of deep blue water and white sands. Alex can't help wondering why Dr. Moreland really invited him to the island. When he probes, Alex discovers a sour and unwelcome truth. But truth it is, and its discovery comes just in time to save Alex and Robin from the violence that threatens them.