Lewis MacDougall
Conor
Sigourney Weaver
Grandma
Felicity Jones
Mum
Toby Kebbell
Dad
Ben Moor
Mr. Clark
James Melville
Harry
O
Oliver Steer
Sully
Dominic Boyle
Anton
Jennifer Lim
Miss Kwan
M
Max Gabbay
Steven
J
Joe Curtis
Peter
Morgan Symes
Lawyer
M
Max Golds
5-Year-Old Connor
Frida Palsson
Lily's Mum
Wanda Opalinska
Female Nurse
P
Patrick Taggart
Teacher
Lily-Rose Aslandogdu
Lily
Liam Neeson
The Monster (voice)
Geraldine Chaplin
The Head Teacher (uncredited)
Jake Talbot
Rollercoaster Boy (uncredited)
L
Lee Bolton
Rollercoster Rider (uncredited)
G
Garry Marriott
Paramedic (uncredited)