This movie was a shocker to me. I believe it is not very often that a movie is released and there doesn't appear to be much of a money-making agenda to it. The film is made and released because the actors / directors / producers want to make something that is GOOD and perhaps a bit different. I think that is what we are dealing with here with The Killing of a Sacred Deer.
For one thing, i will never be able to look at Barry Keoghan the same again. I don't know if it is his acting or the script, or his look, or a combination of the three, but he is terrifying in this.
I am going to be intentionally vague in this writeup because I think that if you appreciate something that is both dark and a little bit different, you are in for a treat with this movie and that can easily be spoiled by me choosing the wrong words.

Colin Farrell plays Stephen Murphy who is a very successful surgeon who has decided to take a special interest in a young boy named Martin (Barry Keoghan) in helping him grieve the passing of his father. At first Martin seems like a good kid and their relationship seems innocent enough. However, very quickly Martin's attitude starts to become more and more obsessive and Dr. Stephen starts to ignore his calls and visits.
This doesn't sit well with Martin and well, he calmly explains that bad things are going to start happening to Dr Stephen's family... and indeed they do.
And that is where i MUST leave it for the sake of not ruining stuff. I will say this: If you don't have the patience to wait for a film to get going then this will likely not do it for you because it DOES take a while for it to get moving. However, if you appreciate a good mind F**K, that is definitely what this movie is in spades.
This trailer is perfect because it reveals almost nothing about the plot. I nearly turned this movie off because it took a bit longer than I like to "get to it." However, much like finishing reading "The LIfe of Pi," the wait ended up being worth it.