Fear in the Night (1947)

The dream is unusually vivid Bank employee Vince Grayson finds himself murdering a man in a sinister octagonalshaped room lined with mirrors while a mysterious woman breaks into a safe It is so vivid that Vince suspects it may have really happened To get the dream off his mind he goes on a picnic with some relatives When a thunderstorm forces his party into a nearby mansion Vince discovers that the bizarre room does exist and it means nothing but trouble