Treated myself to a re-read last night and it is a total keeper! Finalist for the Mary Higgins Clark Award at the 2017 Edgar® Awards presented by Mystery Writers of America for the book most closely written in the Mary Higgins Clark Tradition according to guidelines set forth by Mary Higgins Clark:
The protagonist is a nice young woman whose life is suddenly invaded.
She’s self-made and independent, with primarily good family relationships.
She has an interesting job.
She is not looking for trouble–she is doing exactly what she should be doing and something cuts across her bow.
She solves her problem by her own courage and intelligence.
The story has no on-scene violence
The story has no strong four-letter words or explicit sex scenes.