The Water's Lovely — Ruth Rendell

Weeks went by when Ismay never thought of it at all. Then something would bring it back or it would return in a dream. The dream always began in the same way.

She and her mother would be climbing the stairs, following Heather's lead through the bedroom to what was on the other side, not a bathroom in the dream but a chamber floored and walled in marble. In the middle of it was a glassy lake. The white thing in the water floated towards her, its face submerged, and her mother said, absurdly, "Don't look!"
The dead man was Ismay's stepfather, Guy. Now, nine years on, she and her sister, Heather, still live in the same house in Clapham. But it has been divided into two self-contained flats. Their mother had lived upstairs with her sister, Pamela. And the bathroom, where Guy had drowned, had disappeared.

Ismay worked in public relations, and Heather in catering. They got on well. They always had. They never discussed the changes to the house, still less what had happened that August day. . .

But even lives as private as these, where secrets hang in the air like dust, intertwine with other worlds and other individuals. And, with painful inevitability, the truth will emerge.