The theme in Chapter 1 of Briar Rose is storytelling, and in particular, the telling of fairy tales.
Although Chapter 1 is short, comprising only two pages, the author clearly establishes that storytelling is going to be an important theme in the book. From the very first sentence, when Shana begs Gemma to "tell your story again", the reader gets the sense that storytelling will be a central theme as the narrative unfolds.
Storytelling is an integral part of the relationship between Gemma and her grandchildren. Shana and Sylvia both excitedly draw close to their grandmother in anticipation, and even Baby Rebecca knows that what is coming will be delightful, banging her spoon against her cup and joining in the clamor for a story. Storytelling is something which Gemma does often, and she has a wide variety in her repertoire, as she asks the girls "which one" they would like to hear. The children have heard her stories frequently enough so that they are familiar with them. Shana and Sylvia whisper the words of the opening of the story as Gemma begins, and Rebecca, who can as yet barely talk, repeats the words "none, none, none" as Gemma goes on.
The story that Gemma begins is obviously the children's favorite, and there is a hint that the tale is special to Gemma in a personal way as well. As Gemma talks about the "baby girl with a crown of red hair", she touches "her own hair in which strands of white (curl) around the red like barbed wire", giving the reader a sense that the story she tells involves her in some way, in a way that is perhaps threatening and sinister (Chapter 1).