A Room and an Empty Bed : REMEMBER THIS <i> by Dinitia Smith (Henry Holt: $18.95; 288 pp.)</i>

“Remember This” by Dinitia Smith is a book whose strong suit is plot, told with simplicity and quiet passion, on a haunting subject. The story from a child’s point of view is a testament to the clarity and penetration of which a child is capable, when it comes to the grand figures of her parents and their sins and sensuality and sorrows. The consequences, as well, are dire.

After a somewhat unfortunate first chapter set in the present--unfortunate only in comparison to all that follows--the story is told from childhood through the eyes of an 8-year-old girl. She lives in England though she is American; her father is in the Foreign Service. Her mother seems unhappy in the role of a diplomat’s wife. At a dinner party, the little girl notices a beautiful married woman and in the purity of the child’s view it is apparent that the beautiful married woman is having an affair with the child’s father.

The child’s mother then begins to deteriorate before her eyes. She too knows of the affair. She becomes pregnant again, but it does not save the marriage. Instead she grows ill and dies--as if from sorrow. Afterward, the child knows that her father’s affair is continuing--some nights he does not come home at all--and she looks at his empty room: “She stood staring at the great, untouched room. And the sight of it filled her suddenly with sadness.”

She lives with the burden of her father’s affair with the married woman, Barbara. “Her father and Barbara were so in love, he was caught by her beauty like a moth dazzled by the light. It was as if they were always on a honeymoon, and she, Laura, felt like a witness to some great love story.” The little girl watched her mother die, as if of sorrow, and then must watch the passion of her father’s life, with another woman. The two have declared themselves to the little girl, and they plan to marry as soon as the woman can obtain a divorce.

The woman has a son, a little boy named Simon. He comes to visit, he takes a liking to Laura--they are in the same boat, after all--each has a parent who betrayed them. Simon and Laura sleep together innocently in the same bed--”Here at last was a companion for her nights.”

He had called her “sister.” “He had said that word, given language to the fact that he loved her. If one was a sister, that meant that someone, a brother, or a sister, was protecting you, would never let you down, would love you through all time. Now she had a brother.

“And she knew that she would always love him. What is a brother? she wondered. Your own flesh and blood, your own image. And yet, of course, he wasn’t really her brother.”

A messy divorce proceeding begins for Barbara and an even messier suit attempting to gain custody of Simon. But Simon’s father is enraged and bitter--and apparently emotionally disturbed (nor had he made his wife happy)--he has had detectives follow Barbara during her illicit affair and wins the court case proving her an unfit mother.

Simon is not allowed to visit anymore--a mother loses her child, forfeits him for a great love affair--and a little girl loses her brother and only friend and solace. Meanwhile the child continues in her life overpowered by Barbara’s beauty--for she is a great beauty--and her overpowering love affair with Laura’s father, for which she gave up everything, including her own son.

Laura is sent to America for a year to live with her mother’s mother in a small, honest town unlike the England she had known in her childhood as a witness of illicit passion. She finds that her grandparents are devastated by their daughter’s death, and she herself begins to wonder at it--whether it could even have been murder for the sake of love.

Eventually her father and Barbara move to America. Her father’s career in the Foreign Service was ruined by the scandal, and he takes some innocuous desk job in Washington. The family moves constantly around the environs, for Barbara cannot seem to be content. Theirs was the love of a tragic matinee and it will take its toll. They take to drinking and reclusion.

Laura grows up and moves to New York and becomes a journalist. But she is doomed to commit the sins of her father. She falls in love with a married man, overcome by the physical passion Barbara had once told her she would one day understand. The married man’s wife, who knows of her affair, has a nervous breakdown, they divorce, she loses her child.

Laura takes her paramour to meet her old grandmother in the small, honest town. She speculates on the repeat of the tragedy.

“If she had stayed in Everett . . . she would have existed in an ordered world where obligation came first, even if the personal cost was agony. . . . She would have been like her grandmother, sweet and dutiful. . . . She understood now how (her father) must have hated it, been suffocated by it, longed to escape it, to escape from Ruth, to marry Barbara, who was glamorous and foreign and different.”

Simon, who had long ago disappeared, and of whom she often thought--the sole companion of her childhood--suddenly turns up in New York. He has become a criminal, the casualty of Barbara and her grand matinee love. They destroyed him. For “children are consigned to remember the longest.”

Laura solves the mystery of her mother’s death and in this gripping tale, having pursued the attraction of sin and paid its cost, comes to hope, though it is not an easy ending.