Tulip — Arthur Marx

After UCLA coed Abigail Hunter disappears without a trace from a Caribbean cruise ship on which she and her parents and older brother are vacationing during spring break, her father, millionaire shipping magnate George Hunter, desperate for news of his daughter, hires Dan Grail, a Beverly Hills private eye to investigate her disappearance and offers a huge reward if he is successful in bringing her home successfully. Hoping to get a lead as to her whereabouts, Grail books passage on the same cruise ship from which the girl disappeared. His efforts are unsuccessful at first, but he does pick up some strong clues during the voyage. After some harrowing near-death experiences, he winds up in New York City, where he sees a girl who looks suspiciously like Abbey on a porn site on his computer. Her working name is Tulip. This gives him the idea that she might be in Amsterdam, Holland, which is notorious for its wide-open red light district and pornographic film industry. Eventually he tracks Abbey down, but finding her and rescuing her from the porn studio where she is being held captive nearly leads to his own demise.