William Willis, fakely known as Will Benson, is the hidden secondary antagonist of the 1998 slasher film I Still Know What You Did Last Summer. He is the son and accomplice of Ben Willis, and acted as one of the film's protagonists.
He is portrayed by Matthew Settle.
Will Willis is Ben Willis's son and Susie's brother. Some time ago, the Willis family lived in the Bahamas until Ben killed his wife and moved to Southport with his children. After Ben was run over by Julie James, Ray Bronson, Barry Cox and Helen Shivers during a summer and lost one of his hands because of them one year later, Will decided to help his father to get revenge.
Under the identity of Will Benson, he befriended Julie and her friends and feigned to have a crush on her. One day, Will calls Julie and her roommate Karla by pretending to be a radio host, and tells them that they have won a trip to the Bahamas. Karla invites her boyfriend Tyrell and Will to come with them.
After the group arrives in the Bahamas, Ben Willis begins to murder several people, including Tyrell, and tries to kill Julie. Estes, a baggage handler who has known Ben and his family, recognizes Will and attempts to leave the island, but Will follows him and kills him with a harpoon. He later pretends to be injured so that Julie tries to help him, however she notices there is no wound on him and Will reveals her the truth. Then, he drag her to a graveyard where Ben is waiting for her. Before he could kill her, Ray arrives and fights against Will. Ben tries to kill him with his hook, but Ray dodges the attack which accidently kills Will. The death of his son enrages Ben, however he is shot by Julie a few moments later.