Found: popular author, thriller, kidnapped children

Hello, I am seeking the name of this book, which is probably already in my library- but I forgot to tag it and can't find it.

POSSIBLE TITLE: ___________ THE CHILDREN???

This book was from my mother's collection- so it would have been a very popular book- and this authoress, had many books.

The MC female, mother, had two children that were murdered??? kidnapped?? definitely murdered. I think she recalls seeing their faces wrapped in a plastic bag. There is a scene in which she is probably in shock/ depression and her husband is giving her a bath- and maybe he used to bathe kids too???

I don't recall if she is remarried- but it seems to be happening again

thank u

eg

Should have added: probably written between 1977- 1980

FOUND. WHERE ARE THE CHILDREN. MARY HIGGINS CLARK

Touchstone: Where are the Children? by Mary Higgins Clark