The film was an unauthorized adaptation of Robert Louis Stevenson's novel The Strange Case of Dr. Jekyll and Mr. Hyde, but the source material went unrecognized by some of the German media due to changes in the characters' names. Released in 1920, this is one of Murnau's lost films. While the film itself does not survive, the scripts and related production notes do. Because the film is lost, its full length is unknown. Dr. Warren is the Dr. Jekyll character who changes into Mr. O'Connor, a parallel of Mr. Hyde. This transformation is brought about, not by experimentation with chemicals as in Stevenson's original, but through the supernatural agency of a bust of Janus (the Roman god of the doorway), which Warren / O'Connor purchases in the opening sequence as a gift for his sweetheart, Jane. When she refuses the gift, horrified, Warren / O'Connor is forced to keep the statuette himself...The Head of Janus featuring Conrad Veidt and Magnus Stifter is not currently available to stream, rent, or buy but you can add it to your want to see list for updates. It's a horror movie with a better than average IMDb audience rating of 7.5 (155 votes).