12-year-old Conor encounters an ancient tree monster who proceeds to help him cope with his mother's terminal illness and being bullied in school.
Lewis MacDougall Conor
Sigourney Weaver Grandma
Felicity Jones Mum
Toby Kebbell Dad
Ben Moor Mr. Clark
James Melville Harry
Oliver Steer Sully
Dominic Boyle Anton
Jennifer Lim Miss Kwan
Max Gabbay Steven
Joe Curtis Peter
Morgan Symes Lawyer
Max Golds 5-Year-Old Connor
Frida Palsson Lily's Mum
Wanda Opalinska Female Nurse
Patrick Taggart Teacher
Lily-Rose Aslandogdu Lily
Liam Neeson The Monster (voice)
Geraldine Chaplin The Head Teacher (uncredited)
Jake Talbot Rollercoaster Boy (uncredited)
Lee Bolton Rollercoster Rider (uncredited)
Garry Marriott Paramedic (uncredited)