George MacKay

Character: Jack Marrowbone

Anya Taylor-Joy

Character: Allie

Charlie Heaton

Character: Billy Marrowbone

Mia Goth

Character: Jane Marrowbone

Matthew Stagg

Character: Sam Marrowbone

Nicola Harrison

Character: Rose Marrowbone, Mother

Kyle Soller

Character: Tom Porter

Tom Fisher

Character: Simon Fairbairn, Father

Myra Kathryn Pearse

Character: Molly

Paul Jesson

Character: Doctor

Robert Strange

Character: Monster

Laura Brook

Character: Thelma (uncredited)

Adam Quintero

Character: Mr. Gouldman (voice) (uncredited)