By 1938, Magener was working in Bombay for the German multi-national company IG Farben. At the start of World War II, he was interned in September 1939 by the British. By April 1944, he found himself with 1500 other foreign nationals in a warehouse in Dehradun near the border of Nepal at the foot of the Himalayas. Magener and his friend, Heins von Have, were resolved to escape. They learned that several other prisoners were also planning to escape, among them, Heinrich Harrer, who was part of the four-man climbing team that first scaled the Eiger north face in Switzerland. On the afternoon of 29 April 1944, seven internees made their escape, with Magener and von Have—both of whom spoke fluent English—disguised as British officers.