There are three main characters and a number of less prominent figures in this novel.

Daniel is our protagonist and main character. The novel follows the young Jew's journey from boyhood to manhood against the backdrop of the Holocaust and World War II. At the start of the novel, he is known for his great sense of humor.

Erika is Daniel's younger sister, who is known for her talent on the violin and for being the youngest performer in the Lodz Orchestra. She also composes her own songs, which she refers to as "happy tunes." She is described as being an extremely smart child.

Rosa is Daniel's girlfriend. She is a feisty character, outspoken about her desire to defeat the enemy and prevent the ghetto from descending into pandemonium. She is both an activist and a source of hope for the others.

Other characters in this memorable story include Ruth and Joseph—Daniel's parents. Joseph survives the war, while Ruth dies at the infamous Auschwitz concentration camp.

Daniel's uncle, Peter, is a photographer and professor who was dismissed from his job due to his Jewish faith and later murdered. His wife is Daniel's Auntie Leah, and the couple had four children. One of these children is Friedrich, who ends up being orphaned.

The characters in the book are as follows:

• Daniel: At the beginning of the book, he is a 14-year-old Jewish boy living in Frankfurt, Germany in the late 1930s and early 1940s. He is deported to the Lodz Ghetto during the Holocaust in Nazi Germany and then liberated at the Buchenwald concentration camp when he is 18. At the beginning of the book, he is a comical kid who likes to make jokes.
• Erika: Daniel's younger sister. She is in the orchestra in the Lodz Ghetto and plays the violin. She has wavy brown hair and brown eyes, and Daniel compares her to a mouse when she is little. She is calm and quiet and expresses herself through her music.
• Mother, Ruth: Daniel's mother, who dies at Auschwitz. Her clever handling of food and frugality helps others, and she is described as calm, beautiful, and sweet. 
• Father, Joseph: He is the head of Daniel's family and owns a hardware store. He is a religious man, and his spirit helps other survive. His brothers are Leo, Walter, and Aaron.
• Rosa: She is Daniel's girlfriend and is very spirited. Nathan: Rosa's brother. Rosa starts a youth group in the Lodz Ghetto that Daniel and Erika join. 
• Uncle Peter: A photographer who is fired from his teaching job because he is Jewish. He then teaches at a Jewish school. He is Daniel's uncle, and Daniel is very fond of him. Peter is killed at Dachau, and his ashes are sent to Daniel's family.
• Auntie Leah: Peter's wife and Daniel's mother's oldest sister. Leah is bossy and has four children: Friedrich, Mia, Gertrude, and Brigitte. 
• Adam: A resistance fighter in the Auschwitz camp who is killed when he tries to resist an SS officer. 
• Friedrich: Daniel's cousin who is one year younger than Daniel and who lives near him in the ghetto. He becomes an orphan.
• Opa Karl: Daniel's grandfather who dies two years before the action in the book.
• Oma Miriam: Daniel's paternal grandmother who was married to Opa Karl and who lives in an old age home at the beginning of the book. She makes Daniel a Hitler Youth uniform when he is 12 so he has the freedom to go wherever he wants to. She is funny and smart, and Daniel adores her.
• Opa Samuel and Oma Rachel: Daniel's mother's parents. 
• Mr. Schneider: Daniel's teacher at the beginning of the book who doesn't like his joking around. Mr. Schneider also doesn't like Daniel because Daniel is Jewish. 
• Uncle David: Daniel's uncle who marries a Christian and moves to the United States. He wants the rest of the family to join him in the U.S. 
• Hans: Daniel's best friend when they are little. Hans isn't Jewish and attends another school. 

There are three important figures in Matas' novel about the holocaust.

Daniel is the main character. He manages to survive the the horrors of Hitler. The novel follows Daniel from the age of six in 1933 until he is eighteen, in 1945.

Erika, Daniel's younger sister, is the other main character in the story. Although she is young, Erika has a wisdom beyond her years and tries to make sense of the terrible events that she, her family, and the Jewish people endure.

Rosa is "the girl Daniel met in the Lodz Ghetto, remains focal in his mind throughout his time in the two death camps, but she does not reappear until the conclusion when Daniel finds her alive in Lodz."

A good number of other characters flow in and out of the narrative, but their roles are minor, and Daniel alone remains central to the story from beginning to end.