Dr B. MacRannoch is in the Bahamas with her father who has moved there from Scotland because of asthma. She is a savvy and tough young woman who shows much independence of mind and spirit. However, when Sir Bart Edgecome, a British agent who has been poisoned with arsenic, falls ill on his way back from New York, she becomes involved in a series of events beyond her wildest imagination. Drawn into an espionage plot with multiple suspects, it is only the presence of enigmatic portrait painter Johnson Johnson on his yacht, Dolly , that saves the day. But nothing is quite as straightforward as it at first seems.