McNamara launches her true crime blog, True Crime Diary, and begins investigating unsolved murders online from home.

Ruth arrives to check on her daughter Manuela Witthuhn and discovers her murdered, with blood-splattered walls and marks on her wrists.

Roger Harrington finds his son Keith and daughter-in-law Patty bludgeoned to death in their bed inside a gated community.

The Golden State Killer breaks into a woman's home in Rancho Cordova, wearing a ski mask and raping her.

Detectives Shelby and Daly identify a clear pattern across multiple sexual assaults and name the offender the East Area Rapist.

Criminalist Jim White notices striking similarities between the Harrington and Witthuhn murders and suspects a single killer is responsible.

DNA analysis by criminalist Mary Hong proves one individual committed the Harrington, Witthuhn, and Cruz murders.

Detective Larry Pool has Hong analyze DNA from the Ventura Smith murders, connecting them to the other GSK homicides.

A Goleta couple is tied up by an intruder, but the woman breaks free and alerts her FBI agent neighbor.

Larry Pool approaches the media with the case, and the resulting article names the killer the Original Night Stalker.

Paul Holes and Mary Hong use DNA to confirm the East Area Rapist and the Southern California murderer are the same person.

McNamara reads Sudden Terror by former detective Larry Crompton and channels her investigative obsession toward the Golden State Killer.

Paul Holes takes McNamara on a tour of the Golden State Killer's crime sites throughout Contra Costa County.

McNamara dies in her sleep, leaving the manuscript of I'll Be Gone in the Dark unfinished.

Federal officers arrest Joseph James DeAngelo for the Golden State Killer's crimes following the book's publication.

Michelle McNamara launches a true crime blog and eventually directs her obsessive research toward a serial rapist and murderer who terrorized California for a decade. Detectives identify a pattern across dozens of rapes in Sacramento, naming the offender the East Area Rapist, while murders in Southern California go unconnected for years. New DNA technology in the 1990s finally allows criminalists to prove that a single individual committed a string of apparently unrelated homicides across the state. Paul Holes then uses DNA evidence to link the Northern California rapes to the Southern California murders, confirming one man was responsible for everything. McNamara joins the hunt, meeting key investigators and pursuing leads, but dies before finishing her book. The case is ultimately resolved when federal officers arrest Joseph James DeAngelo for the crimes shortly after the book's posthumous publication.

The Golden State Killer's crimes and the investigation that pursued him.

McNamara discovers vintage cufflinks for sale online that appear to match a pair the Golden State Killer stole from a victim.

David's brother Drew finds a fragment of Manuela Witthuhn's skull beneath her bed while cleaning up the crime scene.

McNamara leaves the Funny People premiere early after receiving an email confirming the capture of a murderer she had been hunting.

A neighbor named Kathleen Lombardo is murdered near McNamara's Oak Park home, and the killer is never identified.

The GSK shifts to targeting couples, binding the man and balancing a stack of plates on his back as a warning device.

Detective McGowen corners the Ransacker at night, and the masked man fires a shot that destroys McGowen's flashlight before escaping.

Dr. Robert Offerman and Debra Manning are murdered in their Goleta home in the months following the failed nearby assault.

Cheri Domingo and Gregory Sanchez are murdered in Santa Barbara, with the GSK taking the ligatures from the scene to destroy evidence.

Orange County DNA analysis links the Domingo and Sanchez murders to the larger pattern of Golden State Killer homicides.

McNamara meets former detective Richard Shelby over lunch and questions him about the police's many failures during the East Area Rapist investigation.

McNamara delivers the cufflinks to Larry Pool, who contacts the victim's family only to confirm the cufflinks are not a match.

McNamara ignores two teenagers casing homes on Thanksgiving, and her neighbor is robbed the following day.

Holes leads McNamara along the GSK's escape route in Danville, where a map with the word PUNISHMENT written on the back was found.

Patton Oswalt gives McNamara a series of watercolor paintings depicting her fighting famous serial killers as an anniversary gift.

Paul Haynes and Billy Jensen write Part 3 of the book after concluding that McNamara's writing style cannot be replicated.

The Golden State Killer's crimes leave a trail of devastated families and frustrated investigators, beginning with the discovery of victims like Manuela Witthuhn and culminating in a series of murders that police struggle to connect. In Visalia, a serial burglar known as the Ransacker terrorizes the community with bizarre, escalating crimes before a confrontation with a detective ends his spree. McNamara pursues her own investigation by trading evidence, meeting detectives in diners and parking lots, and delivering physical leads like vintage cufflinks that ultimately prove to be dead ends. Her amateur sleuthing takes her into the field with Paul Holes and brings her face to face with the human cost of the decades-long case. Paul Haynes and Billy Jensen are left to complete McNamara's manuscript after her death, assembling her drafts into a coherent final section. Together, these secondary events flesh out the full human texture of both the crimes and the obsessive pursuit that defined McNamara's final years.

The victims, the detectives, and McNamara's personal investigation on the ground.

David recalls discovering footprints outside his house months before the murder, and the resulting sketch matches prints found at the crime scene.

McNamara meets Terry Keating, who describes a suspiciously calm man who approached him and friends near the site of Lombardo's murder.

The GSK threatens to kill two people for every report of his crimes that appears in the news.

Following Detective McGowen's nighttime encounter with the Ransacker, the Visalia burglaries abruptly and permanently stop.

Scientists determine that the murderer in the Cruz case fails to secrete blood-group antigens, identifying him as a rare nonsecretor.

Larry Crompton tells Paul Holes he long suspected the GSK in Santa Barbara murders but was blocked by uncooperative local police.

After the DNA link is announced publicly, the GSK calls one of his original victims and asks if she remembers when they played.

Online investigator Paul Haynes reveals he has spent roughly four thousand hours searching directories and yearbooks to identify GSK suspects.

McNamara discovers the GSK regularly traveled through Sacramento's sewer system to gather information about neighborhoods and potential victims.

Holes deduces the GSK may have had access to a private airplane, based on assault locations near two different airports.

Retired detective Fred Ray tells McNamara he is certain he would have recognized the Golden State Killer if they had ever met.

Jim Walther emerges as the most compelling GSK suspect after his biography and travel history align eerily with the killer's known movements.

A homeless man confronted by Sacramento police admits to being Walther and provides a DNA sample that does not match the GSK.

Holes inserts the GSK's Y-DNA profile into a genealogy database and finds a match only with a fellow investigator who uploaded the same data.

McNamara closes the book with a letter addressed directly to the Golden State Killer, declaring he will be forced into the light.

The hunt for the Golden State Killer is defined as much by its frustrating near-misses and sudden revelations as by its headline events, beginning with small details at crime scenes that hint at a larger pattern. The Ransacker's Visalia spree abruptly halts after a detective's flashlight encounter, and biological analysis of the Cruz case reveals the killer possesses a rare genetic trait that narrows his profile. A series of promising suspects—each eerily matching the killer's known biography—are eliminated one by one through DNA testing, including the most compelling lead of all, Jim Walther, who is eventually located homeless and cleared. McNamara's own investigation swings between elation and despair, fueled by online collaborators spending thousands of hours on the case and by theoretical breakthroughs like the GSK's suspected use of a private airplane. At the book's close, cutting-edge genetic genealogy approaches like Y-DNA database searches are attempted but stalled by privacy walls. McNamara's final act is a direct letter to the killer, reclaiming power through identification and vowing that he will be brought into the light.

The key discoveries, dead ends, and emotional shifts that shaped the search for the killer.