Henry’s would later describe his time in South Michigan as a "nightmare that would not end." Almost from the time he was imprisoned, he complained of hearing "voices" in his head that taunted him day and night. The prison's psychologists interviewed him in an attempt to settle him down. Lucas talked freely about the voices inside his head, including his mother’s. "She wanted me to commit suicide for what I done to her," he told them. He blamed his destructive and undisciplined behaviour on her influence. Weeks later, Henry wrote a letter to his sister telling her that he couldn’t stand it any more and was going to kill himself.

Some time later he made good on his threats and slashed his wrists and stomach with a razor blade on two separate occasions. Jail staff thwarted both attempts and he was transferred to Iona State Mental hospital for treatment. What followed were four-and-a-half years of drug and shock therapy, both of which only succeeded in making Henry meaner and more prone to violence. At one stage he told the doctors that if he were released he would definitely kill again.

Regardless of his threats, in 1966, he was transferred back to Michigan State prison. Incredibly, not long after his return, a prison psychologist conducted an examination of Lucas and reported to the parole board that: -

Lucas, on the other hand, was full of vengeance. Driven by the need for revenge, he spent most of his prison time learning the methods of other dangerous criminals. He studied books on police procedures and later, when he was put to work in the prison records room, he studied the files of other inmates analysing the reasons they had been caught. It wasn’t long before he learned that, to avoid detection, all he had to do was keep moving across state lines after each offence.

Four years later, in June 1970, Henry got to put his ideas into practice when he was given early release because of severe overcrowding conditions in the prison. On the day he left Michigan State prison, he told the warders, "I’ll leave you a present on the doorstep." Later, Lucas claimed he murdered two women on the day of his release, leaving one of his victims within sight of the prison walls. Authorities have yet to uncover any evidence to support his claim

Lucas’s newfound freedom didn’t last long. Twelve months later he was back in Michigan State Penitentiary, charged with the attempted kidnapping of a teenage girl from a bus stop and violating his parole by being in possession of a handgun. After serving a further four years, he was released in August 1975, telling prison officials that "this time," he was going to "hole-up somewhere and get a job and make some money." Instead, even though he would eventually find some part-time work, Henry Lee Lucas began to drift around the country. His hapless wanderings marked the beginning of one of the most controversial episodes in American criminal history.