William Turner could always sense the emotions and thoughts of those around him as he was growing up. What he didn't know was that as he was reading these thoughts and emotions he was stealing their life essence as well. William killed his own mother by accident and was placed in an orphanage after his father died. He was a victim of bullying at the orphanage until he realized he had the power mentally to hurt others back.
As an adult William, lived in a secluded part of town where he could quietly live of the psychic essence of his neighbors without notice. He encountered Spider-Man who put an end to his feeding and caused him to be thrown into prison. In prison, Mindworm was cut off from emotional and mental contact from others and slipped into a coma-like state. In this state, he could enter the dreams of others and eventually realized that he was the cause of his parents death.
Depressed, Mindworm slipped into alcoholism when released. While broadcasting his own misery to the neighborhood around him, he was murdered by street thugs.