"Let me tell you a secret. Your nana (grandfather) helped Jewish families escape the Nazis."

That single sentence from his mother set Vinay Gupta off on a journey into his grandfather's past. What he unearthed was a tale more gripping than fiction: a little-known act of heroism by an Indian businessman who risked everything to save strangers in Europe's darkest hour.

This wasn't just compassion; it was logistics, risk, and resolve. Back in India, Kundanlal set up a businesses to employ Jews, built homes to house them - only to watch the British declare them as "enemy aliens" and detain them once World War Two broke out.

Kundanlal's life reads like an epic: a poor boy from Ludhiana, married at 13, who sold everything from timber and salt to lab gear and bullock-cart wheels. He also ran a clothing business and a matchstick factory. He topped his class in Lahore - joining the colonial civil service at 22, only to resign from it all to participate in the freedom movement and a life of building factories.

He shook hands with Indian independence leader and later its first prime minister Jawaharlal Nehru and crossed paths with actress Devika Rani on a steamer to Europe.

In A Rescue In Vienna, a family memoir, Gupta uncovers his grandfather's extraordinary Indian rescue on foreign soil - pieced together through family letters, survivor interviews, and historical records.

In the shadow of Hitler's 1938 annexation of Austria, Kundanlal, a machine tool manufacturer from Ludhiana city in the northern state of Punjab, quietly offered Jewish professionals jobs in India to get them life-saving visas. He offered work, provided livelihood and build homes for those families in India.

Kundanlal rescued five families.

Fritz Weiss, a 30-year-old Jewish lawyer, was hiding in a hospital, feigning illness. Kundanlal was also in the same hospital to get treatment for an illness.

After Nazis forced Weiss to clean the streets outside his own home, Kundanlal handed him a lifeline: a job offer at the fictitious "Kundan Agencies." It got him a visa to India.

Alfred Wachsler, a master woodworker, met Kundanlal while bringing his pregnant wife for tests. Promised a future in furniture and a sponsor for emigration, his family became one of the Jewish households to........

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