It starts with a German adviser (Herr Duckawitz) who is working for the German General Best, who is head of the German occupying forces in Denmark (Denmark was occupied in 1940). He learns that General Best has asked Himmler that he (Best) be allowed to deport the Danish Jews. Duckawitz learns of the exact date 2 days before the Jews will be arrested in a night raid throughout Copenhagen. He secretly warns the Jewish leaders, and one rabbi warns the 80 people during a service at the synagogue. Those 80 then race out around the city to warn all Jews (again some 8,000 people). Almost every Jew gets the warning, and they go into hiding. The Danish resistance organizes rescue routes to get everyone to Sweden (a few miles across a body of water). A large fraction of the Danish population helps to hide the Jews. Many regular German officers and soldiers also help, by canceling all patrols the German Coast Guard during the week when the people are being ferried across to Sweden or by simply "not noticing" people heading to ports with suitcases.
The book also discusses the rescue of some 1,500 Danish Jews from a concentration camp in the Czech Republic. By relentless pressure from the Swedish Red Cross, they first are allowed to get food and then later are simply picked up in a caravan of 30+ buses by the Swedish Red Cross. This is after the Russian Army is in Poland, and they have to travel near the front lines. They travel through bombed out Dresden and are nearby when Potsdam is bombed. The caravan gets hits at least once by artillery, but no one dies.
Overall this was a moving story and an easy read. Probably mostly of interest to those either of Danish heritage or with an interest in the Holocaust.