This attractively attired, believably pursued espionage entertainment begins when Joanna Forest, a ""sensible, ordinary gal"" who doesn't think of herself as dull, and she isn't, is hired to watch and ward over three youngsters on a cruise. Their mother, Mrs. Verriton, is ""delicate"" and she is obviously not enjoying poor health; she's troubled. Their father, Edward, is very charming (the youngsters say he's changed); there's an unidentified dark man, shadowing the Verritons; and then there's some action which leads to an actual attack on Joanna, by Mr. Verriton. . . It is English and accountably well written and it will cosset the younger feminine clientele.