The Angel Spies in Paris

It's 1870 and Dr. Otto A. Brandt is trapped in Paris disguised as a Spaniard while the city is besieged by his fellow Germans. His sister, Amelia, is in prison for spying somewhere inside the walls and is due to meet Madame Guillotine when her child is born. Otto faces winter in a hostile city as starvation grows. Even as he searches for Amelia, he is recruited by the American government mission in its desperate effort to run an escape route for his countrymen and women trapped behind the city's gates. Infatuated with the American spy, Eleanor, Otto is led into the battle zone when she tries to make contact with the Communards. The family mystery about the missing ship: Paper Moon and its Imperial passengers hangs over his head. Can he solve all these problems before time runs out for him and Amelia?
This is untold history. There are real characters and real events here and The Angel Spies in Paris is woven into them. But can you spot the join?