She is the youngest (in terms of age before arrival to the loop) of Miss Peregrine's orphaned peculiar children. She has a mouth at the back of her head which she was at first embarrassed about in front of Jake but then she shows him trusting him.
In Chapter 6 when Jacob is having dinner with the children, he notices that Claire hasn't eaten anything on her plate and asks her why this is so. Miss Peregrine explains that she prefers to eat alone, the other children then begin to pressuring Claire to show them why. Claire gives in and turns around in her chair, dipping her head back to the goose leg on her plate. The mouth hidden by her curls then takes a bite with its "sharped-toothed" jaws.
In Chapter 9 when Miss Avocet arrives at the home, Claire is with the other children in their pajamas outside the sitting room gossiping. She suggests that the peculiars in Miss Avocet's loop might have forgotten to reset their loop, being the first words Claire says throughout the book. When Enoch suggests that the peculiars from Miss Avocet's had been eaten, she and Olive wail. It isn't until Hugh shouts at him and sends his bees after him and Miss Peregrine emerges from the sitting room that he stops.
She stays behind at Miss Wren's Menagerie with Fiona because of a flu she has caught. During the wights' attack, her two mouths were both gagged and she was stuffed into a sack. At the end of the book, it is speculated that she too was captured by Caul's army.
It is confirmed by Addison that the menagerie had been raided by Caul's army, and Claire was captured. However, she was returned safely and without harm. Claire is seen fighting the wights with the other peculiars.
Claire is described as doll-like, with a dainty baby face and fair skin. She has immaculate golden curls that hide the mouth on the back of her head. Like a doll, she is also very small, and is the youngest of Miss Peregrine's wards. She wears a pink dress in the film.
Claire appears to be a shy child. In the movie, she does not talk very much.
Claire's peculiarity is "backmouth", meaning she has a mouth on the back of her head. It is described as being "sharp-toothed", and is masked by her thick golden curls. It is unknown whether or not the additional mouth is able to speak, but it has the ability to eat.
Backmouth is a condition similar to diprosopus, an extremely rare congenital disorder in which parts of or an entire second face is duplicated on the head.
Claire looks up to Miss Peregrine as a parental figure, showing great distraut when she could not get out of her Peregrine form. She also mentions that Miss Peregrine reads her the Tales of the Peculiar. In A Map of Days, Claire is completely against Jacob and Emma's plan of accepting H's mission without Miss Peregrine's permission.
Jacob asks why she isn't eating with the others before the others pressured her into eating in front of them.
Fiona stays behind at Miss Wren's menagerie to take care of the sick. Claire was very upset when she had witnessed a wight push Fiona off a cliff.
Bronwyn is like an older sister to Claire. Claire was there for her when Victor died.
- Claire is the youngest of Miss Peregrine's peculiar children (not counting Jacob).
- The name "Clair" (spelled without the "e") is traditionally a name given to a males and was a popular name in the United Kingdom during the 1970s-80s. Based on this information, it's possible that the photograph "Claire's Golden Curls" is actually of a boy.
- Claire's peculiarity is the same as the Japanese monster Futakuchi-Onna, a woman with an extra face on the back of her head beneath her hair. She also puts her chicken at her backmouth and lets it eat it before putting it back down.