Fiona on the Fourteenth Floor

Published in the US as Mystery on the Fourteenth Floor.

At eighteen years old, Fiona leaves England to join her father in New York. He is a successful travel writer and lives on the fourteenth floor of an old apartment building. His last letter made vague reference to a mystery attached to the building which was engaging his interest - and made Fiona all the more anxious to see him.

On the voyage out, Fiona's cabin is twice ransacked by a mysterious intruder, and on another occasion her handbag vanishes from beside her deck chair. Meanwhile on board she makes the acquaintance of a young New Yorker, Lester Daly, and he becomes her constant companion. It is not until later, alone in NY, that Fiona begins to connect Lester with the "surprise" on board ship, for when the shik had docked, her father was not there to meet her, nor was he at the appartment. Fiona's anxiety grows and the period waiting for news is followed by a series of surprising events.