Horror has in recent years been so informed by found footage, smartphones and Skype that a trend toward folklore was probably inevitable. In Marcin Wrona's film, the mythic entity being awakened is a dybbuk, a spirit of Jewish lore that takes over the body of its host and doesn't let go.
Demon, while not straight horror, has one foot in the genre (the other, of course, is in the grave). Wrona's tale concerns a groom-to-be who, while digging outside his and his fiancée's new fixer-upper of a home, uncovers skeletal remains -- and keeps the secret to himself. This is mythically verboten, it would seem, as by the time Piotr (Itay Tiran) lets anyone in on his discovery the damage is already done: His body is now home to Hana, a Jew whose mysterious death during the height of World War II has entered the realm of local legend.
At first the effects of this possession are subtle enough to disregard as coincidence: a nosebleed during the couple's celebratory wedding dance, strange questions asked of a holy man in attendance. But then the young woman appears to Piotr as he addresses his guests onstage, her skin pale and hair dark. Soon he'll start speaking Yiddish as his body writhes in a futile attempt to reject its new host.
We have a sense of what became of Hana -- you can bury secrets in the ground, but time will eventually bring them back to the surface. With casket-black humor and an eye toward the inescapable ugliness of history, Wrona invokes the ghosts of Poland past.