April's Grave — Susan Howatch

Karen Bennett had fled to New York. She was trying to forget her marriage to Neville. Forget that she had discovered his affair with her twin sister, April.

Now three years later and still in love with her husband, she was suddenly reminded of it all. Including the fact that April had not been heard from since that dreadful day.

What had happened to her? Had she really run away as everyone believed? Or had she met with a more sinister ending? Many people had reason to hate April.

Karen, determined to find out the truth, went back to Neville, to their vacation home in Scotland which held such dear and desperate memories.

And it was here that Karen uncovered reasons to suspect the unthinkable -- that Neville had murdered April....