What makes ordinary people embark upon the extraordinary? While others stood by as the Nazis began their systematic extermination of the Jews, some decent individuals had the courage to do whatever they could to rescue those destined for the gas chambers.

Ida and Louise Cook belong in this honourable category. Along with such better-known heroes as Schindler, Wallenberg and Winton, they, too, deserve to have their story told and retold, for these sisters were instrumental in helping Jews escape from Germany and Austria before the outbreak of war.

Ida Cook's Safe Passage (Harlequin, £8.99) - first published in 1950 as We Followed Our Stars and now reissued with an introduction by Anne Sebba - is the author's account of her own and her sister's exploits. Theirs is a fascinating story, made all the more compelling by Ida's direct, modest prose.

Born at the turn of the last century, Ida and Louise grew up in a loving household where their parents' strict Christian moral code provided the girls with a firm foundation for life.

As passionate opera fans, the sisters travelled to Austria in 1934 and befriended music director Clemens Krauss and his soprano wife, Viorica Ursuleac. They asked the sisters to help one of their Jewish friends get out of Europe, thus setting Ida and Louise on a path which saw them assist at least 29 families to escape to safer shores.

Like other heroes, they deserve to have their story told

Much of the book is devoted to their love of opera. Ida and Louise saved their then meagre salaries for two years to travel to America to hear their favourite opera star.

They became firm friends with several leading singers, and all their savings were spent journeying to America or Europe to hear various performances.

At about the same time as the storm clouds of Nazism were gathering over Europe, Ida, under the name Mary Burchell, was gaining fame as a romantic novelist for Mills and Boon. And Ida's narrative in Safe Passage is also rather romantically expressed; there is an attractive innocence in the storytelling.

Funded by Ida's writing success, she and Louise made numerous undercover missions and became latter-day Scarlet Pimpernels. Their appearance as two rather dotty, eccentric sisters helped allay suspicion.

This, they combined with a degree of chutzpah - Ida once smuggled out of Germany a large diamond brooch belonging to a Jewish woman by wearing it in plain sight on a cheap Woolworth's blouse decorated with gaudy glass buttons.

August 1939 saw an end to their rescue missions, but Ida appeared on TV's This is Your Life in 1956. In 1965, the sisters' work was recognised by Yad Vashem and they were declared "Righteous among the Nations".

Safe Passage by Ida Cook, with a foreword by Anne Sebba, is published by MIRA and is available at http://www.amazon.co.uk/Safe-Passage-MIRA-Mary-Burchell-ebook/dp/B003ZDO...