What kind of secret might be stirring in Papa that Liesel may someday have to keep?

It is difficult to tell you this for certain if I do not have a chapter. Do you know which chapter this is related to? 

Papa is making Liesel keep a secret about the man that is now living in Liesel's home which is Jewish. Papa may end up getting introuble since he is apart of the Nazi party. Papa scared Liesel so he would be sure that she will not tell.