The sleepwalker's world seen through half-lidded eyes, the music, the passion-the elements realized through abstraction in the films of Peter Herwitz-reach full bloom and then some in this wonderful example of Hollywood expressionism. Bernard Herrmann's score is cleverly worked into a plot about a pianist-composer in Victorian London who suffers schizophrenic homicidal periods. Discordant chords bear witness to, indeed seem to initiate, his maniacal moments when he sleepwalks through murder. Director John Brahm, who characteristically directs mysteries of the mind (The Lodger, The Locket) rather than whodunits, here adds music to an array of psychological clues to the murderer's character. It is all played out amid the chiaroscuro effects of lamp-lit fog and the fires of Guy Fawkes day. Laird Cregar, in his last film, plays the Jekyll-and-Hyde role with disturbing conviction. The actor's loss of some 100 pounds before his death-due-to-crash-dieting is evident as Hangover Square progresses.