In the course of the war years, millions of Jews were forced to leave their places of residence, abandoning homes filled with belongings, furniture and memories. At war's end, many survivors returned in the hope of finding family members and their homes themselves, symbolic of life before World War II. Often, they discovered that they could not go home: the house had been destroyed, or emptied, with strangers living inside. The objects that had been such a significant part of their lives had also been taken. Occasionally, they were able to retrieve a few items or documents, but in any event, the world they knew had ceased to exist, and they realized that they would have to rebuild their homes and indeed their world. Katarina Gruenstein née Feldbauer was born in Senica, Western Slovakia in 1944 to parents Frantiseka-Frida and Maurice-Moshe Feldbauer. She had a brother, Bernard. Maurice was a wagon driver and Frantiseka was a housewife who did sewing and baking jobs from time to time. Katarina went to the local religious elementary school, and then to the municipal school and gymnasium.
In March 1942, Katarina and Bernard were deported on the first transport from Bratislava. Some 200 youngsters were on the transport; the boys were sent to the Sered concentration camp and the girls to Petronka, a makeshift camp in an abandoned factory on the outskirts of Bratislava. From there, Katarina was sent to Auschwitz-Birkenau together with approximately 1,000 women and girls. She was assigned to sorting through deportees' belongings and preparing them for shipment to Germany.
On 18 January 1945, Katarina was forced on a death march from Auschwitz to Ravensbrück, and from there to other camps. She was liberated on 9 May 1945. She was the sole survivor of her entire family.
Her father and her mother were murdered at Auschwitz and her brother Bernard at Majdanek. After the war, Katarina returned home to Senica. Her neighbors, the Pokorini family, gave her some photographs and belongings that had belonged to her family. Among the items was a letter, a will of sorts written by her parents, in which they itemized their belongings and details of where they had left them, perhaps in the hope that one of their children would return home after the war and be able to use the belongings to start a new life. The will was written in German, and concludes with a message of love and luck for their children:
"We wish you all the best and much luck,
Your parents, who haven't forgotten you and who love you,
Frida and Maurice"
In December 1946 Katarina married Robert Gruenstein and they started to build a new family.