The film is an adaptation of a popular internet horror concept and urban legend

The ‘Backrooms’ monster torments Clark (Chiwetel Ejiofor) and Dr. Mary Kline (Renate Reinsve), alongside other mysteries—here’s what it all means.

“Backrooms” and “Obsession,” both directed by precocious YouTube-trained talents, breathe shivery cinematic life into urban legends and cautionary tales.