I just watched the Goodnight Mommy and one thing is getting me:
In Goodnight Mommy (2015) On a hot summer day, twin brothers Elias and Lukas (Elias and Lukas Schwarz) welcome their mother (Susanne Wuest) back to their secluded countryside home from what is implied to be a long stint at the hospital, where she underwent some serious plastic surgery.
As the days pass and the mother's behaviour becomes increasingly irritable and erratic, the boys start to question whether it is really their mum who has returned to them. Eventually the boys decide to take matters into their own hands.
This leads to the pair ultimately tying her up and basically torturing her in order to get some answers. In the final moments of the movie it is revealed that Lukas has actually been dead the entire time (he died in an unspecified accident) and Elias is riding delusionally solo.
So, the question becomes, how/when did Lukas die, exactly? The mother explains that it wasn't Elias' fault that his brother died. Why would she feel the need to say this? Did Elias in fact play a (probably accidental) role in his brother's death?