The Water's Lovely by Ruth Rendell

 

Ismay and Heather are sisters and they share a flat.  Their mother and aunt live upstairs as the mother has mental issues.  The sisters are close, perhaps too close, Ismay thinks.  Their mother's troubles started after the death of her husband, the sister's stepfather.  Ismay has always had suspicions that Heather had something to do with that death as the stepfather drowned in the bath and Heather was the only other person home. Ismay wonders if Heather drowned him to protect Ismay from him as he seemed to have more than a stepfather's interest in her.   But nothing was said at the time and now she can't ask Heather about it.

Both of the women have recently found relationships.  Heather has Edmund and she is the first woman Edmund has fallen for.  The two move in together and later marry.  Ismay is madly in love with Andrew but he seems less committed to her. He also desperately despises Heather and Edmund and threatens to leave Ismay unless she gets rid of them.  Then he leaves her anyway for another woman.  When the new woman is found dead, Ismay wonders if Heather is protecting her again.  

Then there is Marion.  Entering her forties, Marion has always had to live by her wits, taking low-paying jobs helping elderly people who she hoodwinks and steals from.  Marion finds out about the earlier death and starts to blackmail Ismay.  How will this play out?

Ruth Rendell specialized in books of psychological suspense.  This book falls into that category.  The reader is drawn into the sisters' lives and the conflicts they are going through.  There are multiple threads, all of which end up being intertwined and satisfactorily resolved.  This book is recommended for mystery readers.