Twenty years ago, Ruby Wax was sifting through her late parents’ attic when she came across a large leather suitcase filled with photographs and documents. There were even letters referring to “Ella” and “Salo”, but the American-born comedienne had little clue as to who they were.

It was just another unknown aspect of Wax’s family history, one that she had struggled to figure out ever since she was a child.

She knew little about why her mother always seemed hysterical, why her father always shouted and why they both remained steadfastly tight-lipped about the Holocaust.

Now those answers have come to light for the 64-year-old actress and author, who delves into her past in next week’s episode of Who Do You Think You Are?

Aside from discovering more about how the Holocaust impacted her parents, Wax also uncovers a family history of mental ill health and depression – something with which she, too, has struggled and which compelled her to retrain as a psychotherapist in recent years.

As the episode begins, Wax describes how her parents, Edmund Wachs and Berta Goldmann, escaped Austria before the outbreak of the Second World War and settled in Chicago.

She recalls that her mother would scream out disconnected thoughts – “the language was nuts” – while her father was volatile.

“He was…as she called him, ‘a torturer’. Obviously they must have had a hideous relationship.”

Ruby as a child with her parents

Ruby as a child with her parents

But her assumptions are soon turned on their head. Travelling first to Vienna, Wax finds out that her father was thrown into prison in April 1938, just weeks after Austria was annexed to Germany, simply because he was Jewish.

Ruby Wax's father Edmund

Ruby Wax’s father Edmund

And one of the now-translated letters from the suitcase reveals her mother wrote to Edmund while he was in prison.

A surprised Wax exclaims: “I had no idea that my mother loved my dad… saying that she cried every day… I had no idea that they really loved each other.”

Another startling revelation is that during his time in prison, Edmund and his fellow Jewish prisoners were tortured. He eventually secured his release, but only on the condition of leaving Austria – or else risk being deported to Dachau concentration camp.

Edmund and Berta hastily married, but she was unable to leave for Belgium with him. He later stowed away on board a ship to the US, while Berta obtained a US visa and the pair were eventually reunited in December 1938.

Wax comes to understand that her mother would have still been in Vienna during Kristallnacht, a series of orchestrated Nazi attacks against Jewish homes, businesses and synagogues, which took place on 9 November 1938.

Comedienne and mental health advocate Ruby Wax;

Comedienne and mental health advocate Ruby Wax

“She never mentioned it,” exclaims Wax. “Do you think that explains why she was out of her mind?”

As she continues tracing her family history, a genealogist reveals that “Ella” and “Salo” referred to in the letters were Ella and Salomen Birer, her maternal great-aunt and uncle. The letters heartbreakingly reveal that the couple had desperately pleaded with Berta help secure a US visa for them.

“You can’t even imagine how afraid we are,” wrote Ella. By the time Berta had the necessary documents to help them, the US Government had changed its requirements and just weeks later, the Third Reich had stopped all emigration.

Ruby Wax's maternal ancestors

Ruby Wax’s maternal ancestors

Wax feels compelled to find out what happened next to Ella and Salo, as well as the rest of her maternal grandfather’s family – a journey of discovery that she feels has finally provided the answers she was looking for.

She quips: “You know, I could have saved myself a lot of time and money. Rather than doing therapy, I should have been doing genealogy. Now knowing my ancestors, I understand a lot more about myself.”

Ruby’s family story is revealed in full on Who Do You Think You Are?, which is broadcast on Wednesday, 4 October, 8pm, BBC One