The residents of a tiny, pre industrial Bavarian village are gripped by a collective madness after the man who runs the local glassworks dies without revealing the secret of the magical Ruby Glass. In their desperation to discover the formula, they turn to superstition and murder. When a mystic appears out of the mountains, will his premonitions save them or foretell their doom? Haunting and visionary, Heart of glass is perhaps best known as the result of one of Werner Herzog's most radical experiments. In order to create the proper atmosphere of trance and sleepwalking, the entire cast acted under hypnosis.