Who was the main characters in book dead girls write letters?

The main characters in "Dead Girls Don't Write Letters" by Cynthia Voigt are:

* Meredith "Mer" Reece: The protagonist, a young girl struggling with the disappearance of her best friend, Helen.

* Helen: Mer's best friend who mysteriously vanishes.

* Jack: A new student who is introduced to the story and becomes involved in the search for Helen.

While the book delves into the lives and relationships of other characters, including Mer's family and townspeople, Mer, Helen, and Jack are the central figures in the story.