portrayed a forensic scientist, having portrayed Will Graham in the 1986 film Manhunter. Development Gil Grissom first appears in CSI: Crime Scene Investigation in the pilot episode. After this he appeared in almost every single episode of the show's first eight years, except in "Hollywood Brass", from season five, an episode that turns entirely around Jim Brass; besides him, only three other regular characters appear. William Petersen did not appear during the season six episode "Gum Drops." This episode was originally going to be how Grissom was convinced that an abduction victim was still alive. When Petersen's nephew died, he flew home and was unavailable for the filming of the episode, which was rewritten to be centered on Nick. During 2007 (CSI season seven), William Petersen took a break from CSI to appear in a five-week run of the Trinity Repertory Company production of Dublin Carol in Providence, Rhode Island, resulting in Grissom taking a sabbatical, being replaced by Liev Schreiber, as Michael Keppler, who developed a small story arc through "Sweet Jane", "Redrum", and "Meet Market". Also in 2007, the character appeared in a two-part crossover with another CBS series, Without a Trace. It was the sixth episode of the sixth season, entitled "Where and Why." The plot of the crossover involved a serial killer that had eluded capture in Nevada and had escaped to New York City. Gil Grissom was brought in to assist in the apprehension. Character background Early life Grissom was born as an only child to a middle-class family in Santa Monica, California. Grissom's father taught botany at a local college and passed his enthusiasm for natural sciences onto his son. His father died when Grissom was nine years old. Grissom recalls the day his father died to Catherine Willows in the episode "Still Life", "He came home from school, one hot humid day, laid down on the couch. I was watching TV, my mom brought in some cold drinks, but she couldn't wake him up. No one would tell me why." Consequently, as a young child, Grissom "played doctor" by performing necropsies on small, deceased animals in the local area. Gil's mother, Betty, who became deaf as a result of the genetic disorder otosclerosis, was responsible for his love of books. As a result of his mother's deafness, Gil became fluent in American Sign Language in order to be able to communicate with her.