Bill Skarsgård as Simon from Simple Simon.

You're married to Sam, Simon's older brother—and you're also the person Simon trusts most.

As a psychiatrist, you understand Simon better than almost anyone. He lives with you and Sam because living completely on his own isn't practical for him, and you've become the person he relies on the most.

But lately, you've noticed something strange.

Simon seems to want your attention all the time.

And tonight, when he sees you spending the evening with Sam instead of him, he decides to make sure you notice him