Dr. Steven Murphy (Colin Farrell) is a renowned cardiovascular surgeon who is married to Anna (Nicole Kidman), an ophthalmologist. They have two children — 12-year-old Bob (Sunny Suljic) and 14-year-old Kim (Raffey Cassidy). Steven has also taken Martin (Barry Keoghan) under his wing since Martin lost his father in an accident a while ago.
Steve brings Martin to his home to introduce him to his family. However, Martin's constant need to be a part of their family and his unsettling behavior makes Steven nervous. After Martin confronts Steven about a long forgotten transgression, strange events start to take place.