Every family has secrets; it's how they are dealt with that determines their power, novelist Grace Wynne-Jones tells Anne Dempsey

As Leo Tolstoy wrote in the first sentence of Anna Karenina: "All happy families resemble each other. Each unhappy family is unhappy in its own way." Perhaps it's the same with family secrets. Many happy families share common jokes, sayings and memories, often operating in a kind of verbal shorthand which makes long explanations unnecessary. Unhappy families often hold secrets too, though these may be of the darker variety, locking siblings away from each other emotionally and/or building protective barricades against what can be said beyond the hall door.

Family secrets is one of the themes of Grace Wynne-Jones's latest novel (her fourth), The Truth Club. The Adams family is not particularly unhappy, but it does have its share of secrets, most notably concerning the disappearance of great-aunt DeeDee, its official black sheep. After her disgrace and departure, she is rarely spoken of again, until grand-niece Sally begins a bit of digging.

"The plot is about Sally learning to listen to herself," says Wynne-Jones. "All her life she has played a role. Stepping out of the role is not a welcome thing; she finds it very difficult because a lot of things don't fit any more. She is drawn to the secrets of the family that she feels need to be solved. Things not spoken of in families are often not fully processed and create a particular atmosphere, as happens here."

Wynne-Jones says her plot themes can arise from issues she may unconsciously need to explore herself.

"My characters tend to lead the novels - they are quite strong, and can give me knowledge I need," she says. "Sometimes an idea is growing until it's ready to pop out. I am fascinated about the human condition, the differing perceptions people have of the same situation. For example, in the book, Sally wanted a mountain bike as a child but didn't get it as her parents were afraid of the danger. By the time her younger sister, April, arrived, things were different, and April got her bike. Sally thought she wasn't as loved as April, but years later when the sisters talked, they discovered that April felt less loved because she concluded her parents didn't care enough to protect her as they did Sally. Telling our family stories can be about our perceptions."

Wynne-Jones agrees that there are all kinds of secrets in families.

"There are happy secrets," she says. "When I stay with one of my brothers, he hides the chocolate where he knows I will find and eat it - and no one has to say anything!

"When I was about five or six, the girl beside me fainted in class, was carried out and fussed over. A few weeks later, I tried it: I just fell over, and was taken out and lain down. I remember thinking, I'm not enjoying this lying here. I began to feel very guilty, the secret building up inside me. Finally, a few days later, I plucked up the courage to tell my father, who reacted quite mildly and told me not to do it again. The relief! I felt it was something I would have to hold for the rest of my life.

"Another big thing with me as a child was my fear of [Soviet leader] Khrushchev. I heard about this bad man and worried about what would happen if I met him. Finally, I told my father, who again laid my fears to rest, which was wonderful.

"It could be important for parents to be aware of what might be scaring children, what secrets they're holding, particularly these days when they can see so much on television they might not understand."

Her own family had not so much a secret as a situation rarely spoken of.

"My mother, Joan de Vere, was born in Eastbourne in 1913 and adopted privately," Wynne-Jones says. "Both the Bishop of Durham and the Bishop of Bath and Wells were involved in the adoption, and she was known as 'castle baby', as she lived for a time in Durham Castle while they decided what would happen to her. Finally, she was adopted by the daughter of the Bishop of Durham and her husband, Stephen de Vere, and went to live in Curragh Chase, their ancestral home in Co Limerick. The house was later burned down in an accidental fire, and is just a shell today, but the grounds are open to the public.

"My mother lived at a time when children were seen and not heard. She had no brothers and sisters, and the housekeeper seems to have been her main emotional support. While never told directly about her birth mother, various things were said or implied. For example, she had a good singing voice, but this was not encouraged and she felt this might have something to do with her own mother.

"My mother told me she was adopted one day when I was about nine or 10. I remember we were driving along in the car. It changes things. I was disappointed and felt dispossessed but glad she felt able to tell me. I used to love going to Curragh Chase, but after that I felt less part of it. But my mother adored it and wrote a booklet, The Abiding Enchantment of Curragh Chase, and other articles which I think had a role in helping to bring the estate to prominence and in supporting its current preservation.

"Over the years as a family we didn't discuss the adoption that often, though my mother was open to speaking about it. However, it was a situation without resolution: she had tried and failed to find out who her birth parents were. Her adoptive mother used to cry whenever approached about it, so my mother stopped asking. Later in life she felt she should have insisted and found out more. She approached an organisation for information, but as it was a private adoption, they couldn't help her.

"She did discover that her mother was probably married at the time of the birth, which cast a whole new light on things but posed new questions as well. My mother wrote about it all in In Ruin Reconciled: A Memoir of Anglo-Ireland, published posthumously in 1990 by Lilliput.

"She died in 1989. Some weeks before, I gave her an article which talked about the feelings of enduring abandonment which adoption can create, and she said it helped."

While there can be many innocent secrets in families, such as where to conceal the box of Black Magic, most big family secrets are to do with sex. In Ireland, keeping the secret spawned the Magdalene laundries for unmarried mothers and the shipping off to the US of children born outside wedlock. Telling the secret today has led to widespread revelations about incest.

Wynne-Jones recalls working as a journalist 20 years ago and interviewing a young single mother who had moved to Dublin from the country to avoid local shame, so allowing the family keep its secret.

"It was huge and sad," she says. "Very many women found themselves alone. There was, and still is, I think, so much sin put on the woman. Women are the carriers of the sin. It is the same with my scapegoat, DeeDee. In some ways, she was too big for the family. They did not know where to put her, and so she left. However, the unspoken can still live on, and what a family does not talk about can become very powerful."

At the same time, she feels there is a place for discretion and privacy.

"I think the nature of secrets has changed, and today we are into their commoditisation with all these reality television shows, celebrities having sex with people in public, selling their privacy for fame," she says. "It can be addictive viewing, a substitute for community, permitting some people to live vicariously through what they see on screen. But just as we can have a toxic, too self-critical shame, so there is a need for a healthy shame around some acts which should be private and are not.

"We all have secrets. We all have stories to tell about our lives. But we are more than our stories. I think knowing our story gives us a chance to change it, not to be limited or victimised by it, nor to overly identify with it. What I'm saying is: we create our own reality and how we hold on to our family secrets or learn to let them go can have a role to play in this."

The Truth Club, by Grace Wynne-Jones, is published by Tivoli, €9.99