Steven (Colin Farrell), an eminent cardiothoracic surgeon is married to Anna (Nicole Kidman), a respected ophthalmologist. They are well off and live a happy and healthy family life with their two children, Kim, 14 (Raffey Cassidy) and Bob, 12 (Sunny Suljic).

 Steven has formed a friendship with Martin (Barry Keoghan), a fatherless 16-year-old boy whom he has taken under his wing. Things take a sinister turn when Steven introduces Martin to his family, gradually throwing their world into turmoil and forcing Steven to make a shocking sacrifice or run the risk of losing everything.