The Hook Killer is a legendary murderer and/or stalker from the urban legend known as the "Hook" - this legend focuses on the plight of a couple of young lovers who drive to a secluded area and try to either have sex or a drunken night out only to be terrorized by the sounds of scraping across their car.
A couple stops her, the boy turns on the radio and they start kissing, but the music is interrupted by a news cast saying that a killer with a hook as one of his hands is on the loose, that he is extremely dangerous, and advises everyone to be careful. The girl was scared and told her boyfriend to take her to her house, but after asking him a couple more times and turning the music back on they went back to kissing. Later they hear scratching noises on the car, the girl gets scared again and tells her boyfriend again numerous times and the boy starts the car and they get back to the girl's house. When they got back to her house, the boy got out to open her girl's car door, and he finds a dangling hook on the car handel.
The Hook Killer is an inspiration for the serial-killer in "I Know What You Did Last Summer" and is considered one of the most famous urban legends of all time.