You are the murderer.  As soon as Mr. White arrived, you thought that he looked familiar, but you could not place him.  On the second night you awoke in a cold sweat and realized how you knew his face.  He was the man in the police drawings of Jack the Ripper.
 
In a rage, you decided that he would die painfully before another night passed.  You distilled a botanical poison that would induce knifelike paralysis and slipped it in his glass of wine.  Unless he was autopsied by an expert, his death would have looked like a heart attack.  Unfortunately, your plans were foiled when someone else – for unknown reasons -- clubbed the body over the head and the authorities were called in.