Dr Jennings, was a German scientist living in America during the events of Sky Captain and the World of Tomorrow. In the early years of the 20th Century, he worked for Dr Totenkopf at Unit 11, helping him to design and create his machines as well as with his less savoury projects.
"I was one of seven scientists chosen to serve at a secret facility just outside Berlin before the start of the First World War. It was known simply as Einheit Elf, Unit 11, we swore never to discuss what went on behind those doors. The things we were made to do there... terrible things..."
Dr Jennings was the last Unit 11 scientist to be caught by the Machines. But, unlike the others he did not escape with his life and he died in the arms of Polly Perkins after being attacked in his laboratory by Totenkopf's Assassin. Before his death however, he did have the courage to seek out Polly Perkins and tell her of the danger the world was now in.