Insidious follows a family whose son ends up in an inexplicable coma. They discover that this coma isn't medically caused, and their son is actually in danger from a malevolent spirit with much more... insidious intentions. (See what I did there? Ha!) The film features a lot of really good, terrifying scenes that are legitimately scary as opposed to just designed to make you jump and spill your popcorn.
After their son falls into a coma, a family moves from their supposedly haunted house and realize after their move that their son has been possessed by evil spirits.