Fear of the Dark (2003)

Twelve year old Ryan Billings has been diagnosed with an acute fear of the dark. He spends each night lying awake in torment, waiting and watching as the evil in the darkness grows stronger, feeding off his fear. His older brother Dale, suspects that there is nothing wrong with Ryan and that this is just a ploy for more attention. Regardless, he promises to watch over his little brother as their parents head off to a party for the night. Outside a storm rages and when the power goes out, darkness envelops the house. Ryan knows that tonight the evil has finally come to claim him. Dale desperately tries everything to try and calm him down, until the horrors in the dark make him realize Ryan had good reason to be so afraid!

Unfortunately the movie Fear of the Dark is not yet available on HBO Max.