We are in Iran in the 80s and there is war going on outside with Iraq. A disheartened mother is stuck with her daughter in their apartment as the threat of missile attack looms. This is a pretty good setup by itself but Under the Shadow adds a supernatural wrench to the gumbo where we don't really know whether the mom is the Babadook or something else is going on.
Its too bad it took what felt like half my adulthood to get past the setup because once it did, Under the Shadow was an effective ghost story aided by a claustrophobic lens that heightens the intensity. But effective only gets you so far and that paired with such a slow start equals only adequate.