The Dark Ocean

Betty Haverhill, an attractive California girl, begins a coming-of-age sojourn, embarking from San Francisco on an Italian freighter bound for ports in El Salvador, Panama, Venezuela, Spain and Italy. To her dismay, the passengers include Ted Bunpole, a former boyfriend who infuriates her by introducing himself as her "fiancé", a notion of which she immediately disabuses both him and her fellow passengers.

Betty develops an attraction for and engages in a mild flirtation with Mik Finsch, an older, mysterious man-of-the-world, but when she accepts an offer of drinks in his cabin, his amorous advances become unacceptable to her and Betty has to fend him off. Ted bursts into Finsch's cabin and the two start fighting; by the time the captain ends the fight, Ted has thrashed Finsch, who claims he was "just warming up".

Betty tells Ted that she could have managed the situation herself and that she still has no interest in marrying him and wishes he had not come. Another passenger tells Betty that Finsch's pride has been wounded and he will get revenge on Ted somehow. That night, Ted becomes missing and a typewritten suicide note is found. There are suspicions, but not any proof. When another "suicide" involving Finsch and the wife of a shipping agent leaves no doubt in Betty's mind that Finsch is a murderer, the two become enemies, with Finsch seemingly having the advantage.