By the time he was thirteen, Henry was almost completely obsessed by sex. He began to trap animals so that he could use them in his private sexual rituals, often torturing them to death. Bestiality became normal behaviour. At about the same time he began to steal more regularly, sometimes for food but more increasingly for money. Later Henry would brag that he murdered for the first time in 1952, aged just fourteen.

Lucas told of how he had abducted a seventeen-year-old girl from a bus stop and beat her until she was unconscious. He then dragged her to a secluded spot and attempted to rape her. When the girl woke and started to scream, Henry strangled her until she lay still. He claims that he had no intention of killing the girl and told interviewers that it took him a long time to get over the "terrible thing" that he had done. To date, there is no record of such a crime having been committed.

Not long after the event, Henry’s brother ran off and joined the Navy. After he left, Henry spent less and less time at home. Most of the time he wandered aimlessly through the district looking for trouble. It wasn’t long before he found it and was subsequently arrested for breaking and entering. He was convicted and sentenced to the Beaumont Training School for Boys in Virginia. The institution records indicate that while there, Henry was disruptive and made numerous escape attempts. He later formed an alliance with a black inmate and, according to prison authorities, the relationship was "of a sexual nature."

One year later he was released. The records of his stay in Beaumont describe him as being friendly one minute and broodingly dangerous the next. The day after his release, Henry bragged of raping his twelve-year-old niece. For the next nine months, he worked as a farm hand, learning various skills until he was picked up for breaking and entering a second time. He was convicted and, because he was now an adult, sentenced to serve four years in Virginia State Penitentiary.

Henry seemed to adapt to prison life, learning trade skills and spending much of his time working on rural road-gangs. In May 1956, while on one such assignment, he escaped and stole a car and drove to Ohio. He was on the run for just two months until he was arrested for transporting stolen property across a state line and sentenced to serve thirteen months in Chillicothe prison in Ohio. During his brief spell of freedom, he met a girl named Stella.

After his release in September 1959, he moved to Tecumseh, Michigan to live with his half-sister Opal. While there, he contacted Stella and after dating her for a short time, asked her to marry him. She agreed and they announced their engagement. Shortly after, Viola came to visit and tried to persuade Henry to leave Stella and come back and live with her, as she was getting on in years and needed someone to look after her. Henry refused and a violent brawl erupted. Stella, realising that this was a family that she didn’t want to be involved in, broke of the engagement and left.

Henry stormed off and went back to Opal’s apartment. Viola followed and the argument continued. At one point Viola hit Henry over the head with a broom and broke it across his skull. Henry retaliated and struck Viola on the neck. He later told police:

Thinking that he had killed his mother, Lucas panicked and, after turning out the lights in the apartment, got in his car and drove to Virginia. As it turned out, Viola hadn’t died after the attack. She was still alive forty-eight hours later, when Opal returned to the apartment and found her lying in a pool of blood. An ambulance was called but, because of the length of time that she had been bleeding and the resulting shock, they were unable to save her and she died a short time later. The official police report stated that she had died of a heart attack, precipitated by the assault.

Henry was later picked up by police in Toledo, Ohio and returned to Michigan and charged with second-degree murder. Despite assuring police that he had acted in self-defence, he later pleaded guilty and was sentenced to 20-40 years in the State Prison of Southern Michigan.