A mentally unstable man who doesn't have a firm grip on reality must investigate whether or not he's a serial killer. A mentally unstable man who doesn't have a firm grip on reality must investigate whether or not he's a serial killer. A mentally unstable man who doesn't have a firm grip on reality must investigate whether or not he's a serial killer. A mentally unstable man who doesn't have a firm grip on reality must investigate whether or not he's a serial killer.