This book is very much like a documentary, in that it follows the event of Daniel's life rather than a traditional plot, which would follow the development of a particular conflict.

However, in these incidents, it is obvious that Daniel's Story is one about the coming of age of a boy stuck in war-torn Europe.  As a boy who is maturing,  he has to decide what type of person he will be.  He can choose to remain bitter and angry and to retaliate against those who have persecuted him and his family.  Or, he can choose to rise above it and to be a better, stronger person than his enemies.

Daniel chooses the latter.  He chooses to be good.  That choice is the climax.  It happens after Buchenwald is liberated.  Daniel threatens to kill the children of an SS officer, but he is unable to do it, and he is angry at himself for causing fear in the children.  He has, as Erika wanted him to, chosen love.