by Louis Lowry, talks about World War II and how those victimized in society still managed to help one another, particularly in the case of Jewish people escaping from Denmark.

Code language was one of the many ways people used to communicate, especially when the Danish people who resisted the German occupation of Denmark attempted to deliver messages or carry out plans of escape to help Jewish people escape to Sweden. 

Since the way to help Jews escape was by hiding them in boats, the only way to safely help would have been by having a fisherman, such as Uncle Henrik from the Johansen family, prepare the way ahead and convey the message that "the coast is clear," meaning it was safe to bring people for transportation. For this, they used the following code: 

Tomorrow will be a great day for fishing.

Once Annemarie Johansen heard this, she would know immediately that it was a safe time to smuggle the Rosens, or any other family that needed to escape, out of Denmark. 

When it was time to bring Ellen out, Mr. Johansen said that he would send his wife for "a visit" along with "a carton of cigarettes." Annemarie again noticed the weirdness of it, as cigarettes had been out of sight for a while. This is when she realizes it was time to deliver Ellen and help her escape. Ellen was "the carton of cigarettes."

Now, in a hypothetical situation, code would be equally necessary. 

The reality is that one would have to use code for everything during the occupation. All of your actions are monitored, and the Germans completely disregarded the basic rights of any citizen. If you had a friend who was Jewish and you were part of the resistance, you would have needed to change your entire method of communication to divert the attention of the people around you. You would have not wanted any eyes on you; basically you and your friend had to be watching out for anything that was said outside of the immediate circle. You had to learn to trust, and that was surely the hardest part of it all. 

Lois Lowry's Number the Stars shows the extreme measures that Jews had to go to during the Second World War to escape territories occupied by the Nazis. Since travel is restricted for Jews, and they will be arrested by the Nazis if they are discovered, they have to sneak out with the help of allies in the resistance.

Annemarie's uncle, Henrik, and her parents are active in the resistance, as was her sister Lise. At the end of the book, the family stages a fake funeral to smuggle clothes and supplies to Jewish families in the casket. Once they are well-stocked for their journey, they are smuggled into Uncle Henrik's fishing boat. Henrik tells Annemarie that:

They had to be absolutely quiet for many hours. The baby was drugged so that it wouldn't wake and cry.

The Jewish families have to stay silent and still to avoid detection as soldiers search the boats.

In addition, the Resistance has created an extra layer of protection to sneak out the Jews. The Nazis have started using sniffer dogs to uncover Jews that have been concealed on the fishing boats. However, with the help of some scientists allied with the Resistance, they have developed a solution which Henrik tells Annemarie about:

And they have created a special drug. I don't know what it is. But it was in the handkerchief. It attracts the dogs, but when they sniff at it, it ruins their sense of smell. Imagine that!

The fishermen keep these drug-laced handkerchiefs on them to attract the dogs and mess with their sense of smell. This keeps the dogs from smelling the concealed Jews and allows them to escape undetected.