Billy Hargrove

Nationality: American
Date of birth: March 29, 1967
Place of birth: California, Ohio, USA
Family
Neil Hargrove (Father)
Susan Hargrove (Stepmother)
Max Mayfield (Stepsister)
Gender: Male
Age: 17 years old (Season 3)

As a child, Billy loved surfing, and his mother supported this passion and spent time with her son at the beach. However, the family's idyllic life was marred by the cruelty and aggression of Billy's father, Neil. He physically abused his wife, and she was eventually forced to leave him and their son. Neil's violence against his family had a significant impact on Billy, turning him into a young bully who beat up other children. Sometime later, Neil married Susan, the mother of Max, whom Billy introduced as his "new sister," a woman he disliked.
In 1984, Billy and his new family moved from California to Hawkins, where he began high school.

At school, many girls immediately set their sights on Billy, who were attracted, among other things, by his car.
On October 31st, Billy was waiting for his stepsister to ride home with her again. After scolding her yet again for being late and telling her that next time she'd have to skateboard home, he brought up Hawkins. He was certain she was to blame for the move, which he, apparently, was not very happy about. He nearly hit Mike, Dustin, and Lucas, but Max managed to turn the wheel in time, saving the lives of her new classmates. At school, a rivalry was slowly developing between him and Steve. Billy tried to accuse Steve of being far worse than him in everything from sports to dating. Furthermore, Billy was against Max socializing with anyone. After seeing Lucas around her several times, he told her there were many people in the world she should avoid, and Lucas was one of them. He was getting ready for a date when his father and his wife returned home. Discovering that Max had escaped through the window and Billy had no idea where his half-sister was, Niall became extremely angry with his son and became physically violent, unable to contain his emotions. In a commanding tone, he told Billy to forget about the date and find his sister. Without hesitation, Billy found the Sinclairs' house and, learning that the boys usually spent their evenings at Mike Wheeler's house, went there. He flirted shamelessly with Karen Wheeler before heading to the Byers' house. Steve met him at the door, insisting his sister wasn't there. But curious children were peeking through the window at the older boys, so Billy rushed inside. A fight broke out between the boys, which Steve initially dominated but eventually lost. To save herself and her friends, Max injected a sleeping pill into her stepbrother's neck and later ordered him to leave her and her friends alone, threatening him with a bat.

In the summer of 1985, Billy began working as a lifeguard at a local pool. Being in good physical condition, he attracted a lot of attention from women, particularly Karen Wheeler. Billy also showed a particular interest in Karen, and while flirting with her, he invited her to "private swimming lessons" in an attempt to seduce her. She agreed to meet him, but before leaving the house, she changed her mind, not wanting to jeopardize her family relationship. Unbeknownst to Billy, on the way to the meeting, he suddenly lost control of his car and crashed into something. Upon exiting the car, he became the victim of the Mind Flayer. From that moment on, Billy began to submit to the monster's will. The next day, Hargrove came to the pool feeling ill. While sitting in the lifeguard's chair, Billy suffered a severe sunburn from exposure to direct sunlight. He went into the shower and began screaming in agony before curling up on the floor. Hearing screams, Heather comes to check on Billy, but he attacks her. Her consciousness is subsequently taken hostage by the Mind Flayer. Some time later, Billy and Heather help render the girl's parents unconscious, becoming the monster's latest victims, whose physical bodies it has been using to develop its powers. Using her powers, Eleven spies on Billy and discovers he has been captured by the Mind Flayer. Using a dummy and a walkie-talkie, Eleven, Max, Lucas, Will, and Mike lure Billy to a sauna near the pool to burn the monster out of Hargrove. Enraged, Billy screams and demands that the teenagers free him. He manages to manipulate his stepsister's emotions and lure her to the door, but then uses a shard of broken glass to threaten her life. Using superhuman strength gained from his contact with the Mind Flayer, Billy breaks through the sauna's closed door and battles Eleven.

The girl throws him out into the street, smashing his body through a wall. Billy hides in a steel mill, where Heather speaks of the army the Mind Flayer has already amassed. Later, Eleven visits Billy again in her visions to find out what happened to him. The girl sees him sitting in his room, but then other images appear. Eleven finds herself on the beach next to Billy's mother, watching her young son surf. Eleven also witnesses Hargrove's memories of being abused by his father throughout his childhood, and then, like him, Billy himself became a bully. Billy ends up near a shopping mall when Jonathan Byers and Nancy Wheeler try to drive away from the building possessed by the Mind Flayer. After Nancy and Jonathan finally manage to start the car, Billy drives straight at them, but is struck by Steve Harrington and Robin. Jonathan, Nancy, Steve, Robin, and Lucas head to the station wagon while the Mind Flayer pursues them, and Eleven, Max, and Mike flee back to the mall. Billy follows them and corners them in the mall's back room. He knocks out Mike and Max, takes Eleven, and returns to the center of the mall to hand her over to his master. Eleven's friends come to the rescue, bombarding the monster with fireworks, while Joyce Byers and Jim Hopper attempt to close the Gate.

Billy is quite attractive to the opposite sex, but he can also come across as unfriendly. He views Steve as a rival he must overcome, so he acts cynically and calculatingly toward him.
Billy drives a blue Chevrolet Camaro, steals other people's girls, and boasts a knack for drinking. Despite this reckless attitude, Billy struggles with problems at home: his father's abusive behavior, which he takes out on Max. However, in 1985, when Eleven gets inside his head, he appears as a friendly and happy child with his mother. This suggests that Billy's character has been hardened by his mother's abandonment and his father's harsh upbringing.