Movie thrillers and mysteries usually revolve around a "McGuffin," an art of fiction set up to establish the plot and motivate the characters but which matters very little by the end of the movie. It's the trap the filmmaker sets to capture the audience to invest them in the story he/she wants to tell.
In this movie, the McGuffin is the mystery itself. The filmmaker doesn't ask us to believe that a ghost can impregnate a sad and grieving girl. Instead, it asks us to look at how loss can become grievance and become toxic, and what it takes to remember who and why we love.
Give it a chance.