Under Full Sail — C.L.R. Dougherty

When Connie and Paul find an amnesia victim stranded on a deserted island, their vacation is spoiled. They were excited about exploring the isolated spot by themselves until the castaway appeared. Who is he? How did he get there? Will he recover his memory? He can't answer their questions, but he needs their help. How he got to Isla de Aves is a mystery. Connie and Paul invite him aboard their charter yacht and sail to Dominica seeking medical attention for him. As snatches of his memory return, he recalls having spent time in St. Lucia. When they take him there, hoping it will stimulate his memory, the trouble begins. Why are people trying to kidnap him? And who's trying to kill him?