The killer in the original 1997 film I Know What You Did Last Summer is Ben Willis, the fisherman who was accidentally hit by the four friends in a car accident the previous summer. He seeks revenge on them for the incident and the death of his daughter, Susie Willis. Ben Willis is the faceless, hook- wielding man who stalks and kills the friends throughout the movie

. In contrast, the TV series I Know What You Did Last Summer features a different killer. In the series, Margot is revealed to be the killer, responsible for multiple murders as part of a complex plot involving identity and secrets among the characters

. So, for the original film, the killer is Ben Willis, the fisherman. For the TV series, the killer is Margot.