I'll Be Gone in the Dark: One Woman's Obsessive Search for the Golden State Killer is a true crime account by author Michelle McNamara. The main characters of I'll Be Gone in the Dark include:

The Golden State Killer, who is also known as the Early Bird Rapist, the East Area Rapist, and the Original Night Stalker. The Golden State Killer is a serial murderer and sadistic rapist who who committed heinous crimes in and around Orange County, Sacramento, and various other locations in California between the years of 1974 and 1986.

Michelle McNamara is the author of I’ll Be Gone in the Dark. McNamara is a talented investigator and writer whose efforts lead to the eventual identification and capture of The Golden State Killer. The book was published posthumously in 2018 after the author mysteriously died in her sleep before finishing the book. McNamara’s friends and colleagues Paul Haynes and Billy Jensen write the third and final section of her book after her untimely death.

Manuela Witthuhn and Patty Harrington, who we are introduced to in the first chapters, are just two of the more than fifty murder victims said to have been killed by The Golden State Killer.

Janelle Cruz, a young woman who is brutally beaten to death by The Golden State Killer.

Linda Sheen is a realtor who finds Janelle Cruz's body.

Terry Keating is an old friend of McNamara's who meets with her to relay information surrounding him finding a woman's dead body.

Criminalist Jim White who works for the Orange County Sheriff's Department and notices similarities between the murder cases of Manuela Witthuhn and Patty Harrington.

Mary Hong, a criminologist who works is the same department at the Orange County Sheriff’s Department as Jim White.

Larry Pool, a sex-crimes detective in Orange County, who works with Mary Hong and Jim White on the case.

Richard Shelby and Carol Daly are two detectives assigned to the case investigating nine attacks that occured in Sacramento over a six month period between 1976-1977.

Dr. Robert Offerman and his wife Alexandria Manning are both murder victims of the The Golden State Killer.

Paul Holes, a criminalist who creates a profile for the killer and works with Mary Hong on the case.

Paul Haynes, also known as The Kid, becomes McNamara’s lead researcher and helps compile the final chapter of her book after her death. A member of an online collective dedicated to compiling evidence and theories related to serial killers.

The Social Worker is a female member of the online amateur sleuth collective who McNamara meets with.

Fred Ray is a former Santa Barbara detective who McNamara meets with. Fred Ray states he may have interviewed The Golden State Killer at one point during his career.

Billy Jensen is an investigative journalist who works with Paul Haynes to compile the third and final chapter of I’ll Be Gone in the Dark.

Debbi Domingo, a troubeled teen, whose mother, Cherly Grace Smith, is murdered by The Golden State Killer.