Like any good horror film participants, Kelly and Ben are dismissive at first, trying desperately to explain away the strangeness, hoping it will go away and they can move on with their lives, especially Ben. Which is odd because several years earlier Ben was part of a science experiment which attempted to contact a ghost and instead released a malevolent entity into our world that killed his girlfriend at the time and was never re-captured. Despite knowing that Ben refuses to admit that the two supernatural elements are related to the extent of trying to talk his new girlfriend into staying in the house even after she's gotten so scared she wants nothing to do with it.
It's that sort of rampant stupidity which bogs The Apparition down into a pointless exercise of slow camera moves and menacing strings and bangs, with no imagination or entertainment on display. First time director Todd Lincoln has lumped various haunted house clichés together, thrown them in a bag, jumbled them up and tossed them against the wall to see what will stick. There is a menacing tone and the odd well designed sequence of terror, but for the most part it is mind-numbingly forgettable. Part of that is because Lincoln has bravely decided to make his characters as bland as possible so that they can't distract us from how ridiculous the plot is.
To her credit Greene does the best she can with what she's got, but mostly that means mixing fear with earnestness, except for the odd discursion into Kelly and Ben's relationship slowly breaking down as she learns what sort of danger he has put her in the path of. That would probably work better if the relationship came off as interesting; unfortunately Ben only seems capable of being sullen. Worse, the more we learn about what he knows, the more stupid his actions appear, making it very difficult to care about him or anything that happens to him.
Once they do finally admit that their house is haunted, and realize that the ghost involved seems to be following them even after they leave, Ben finally breaks down and calls his hold friend Patrick (Tom Felton, Harry Potter) who provides some of the only lift The Apparition gets as he blows into town in his glasses and scarf and begins rattling off a truly impressive slab of bullshit about negative magnetic fields protecting his brain. Channeling every mad scientist since Dr. Frankenstein, Felton passes on even attempting at making the pseudo-science mumbo jumbo he has been given sound legitimate and instead seems focused on just how fast and energetically he can get it out. And it works more or less; it's easy to think the characters are in this situation because at one point they decided to listen to the ideas of a schizophrenic who lives in a cage in his basement.
But he's not in the film anywhere near long enough to make it interesting, coming across more as an afterthought than anything else. Despite the long history of failures that come when filmmakers decide that thinking up some visually interesting set pieces and then creating just enough story to tie them together is all that you need, it doesn't seem to stop anyone from making that same mistake over and over. Because, like buying a lottery ticket, every so often it works out. So despite the odds everyone keeps buying that ticket, thinking they're going to be the lucky one who wins big.
The Apparition is not one of the lucky ones.