Apostle (2018)

A man heads to a remote island in 1905 to find his missing sister, who was supposedly taken by a mysterious cult. Posing as one of the faithful, he slowly pieces together the groups twisted beliefs and the real reason they 've isolated themselves. Things get more tense as the cult 's leader grows suspicious, and brutal punishments are dished out to anyone who strays. As the man digs deeper, he uncovers the violent, decaying core behind their so-called faith. What starts as a rescue mission turns into a grim fight for survival as the island reveals its horrors and the cult tightens its grip. The deeper he goes, the bloodier things get.