Soft in the Shadows by John Turner

Cover copy reads: 'They were the closest of friends--the husband, the wife, the overnight guest.'

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From the back:

A widow so young...

They were her friends and they asked her to stay with them in her moment of grief. A cruel act of fate had left her alone and unprotected and confused... and so she accepted. She knew it was wrong but she needed to forget the hurt and pain and loneliness. She let them take care of her, give comfort to her, until she realized that they had become rivals for her attentions. They were man and woman, husband and wife, and yet they both wanted her to be something more than a guest, something more than a friend.

A triangle which defies description