Who is in the casket in number stars?

In "Number the Stars" by Lois Lowry, the casket contains the body of Peter Neilsen, a young man who was part of the Danish Resistance against the Nazis. His death symbolizes the sacrifices made by those fighting for freedom during World War II. The casket is a poignant reminder of the dangers faced by those who opposed Nazi occupation and the cost of bravery in the face of oppression.