Larissa’s ex is named Chandler Gray. When Jane asks Mistress to see if her police contact can find information on him, the group learns that the police have apparently been working that angle and found out that Larissa called Chandler nearly 24 times on the night she died. The group decides to share this bit of information with the entire Real Crime Network. The forum goes wild, and various people share their investigative plans.

In retrospect, Jane notes that feeding the clue to the entire network would prove to be a mistake.

The internet explodes again, this time in condemnation of Chandler Gray. Jane is unsurprised: Chandler is an affluent frat boy and a serial cheater. She knows that some of the backlash is unwarranted, but the sleuthing community looks down on fraternities, seeing them as “cesspools” of toxic masculinity and racism. Moreover, Chandler and Larissa appear to have had an unstable relationship and argued often. Larissa grew up with few resources and one parent in and out of rehabilitation. She was a serious person and was dedicated to her schoolwork: For her, education was a way out of poverty. No one thinks she deserved a boyfriend like Chandler.

However, when the police discover a shoe print at the crime scene, it does not match Chandler’s. Meanwhile, more details about the crime emerge: Madeleine and Anastasia partied at a local bar until two o’clock in the morning, went home, ordered a pizza sometime after three o’clock, and appear to have fallen asleep. Details are thinner about Larissa’s night out, but she was also home and in bed when the killer snuck in around five o’clock. All three women were brutally stabbed. The killer did not target the fourth roommate, Harlow.

Harlow reports that on the night of the murders, she repeatedly asked Madeleine and Stacie to quiet down, as she was trying to sleep. The last time she came out of her room to yell at them, she saw a man walk by her in the hallway wearing a ski mask. He slipped out of the sliding glass door, appearing familiar with the house. She assumed that it was one of the other women’s friends and went back to sleep. The next morning, without discovering her roommates’ bodies, she texted a friend to come over. More than a half hour after he got to the house, Harlow called 911.

Much will be made of this timeline, but for the moment, the internet remains fixated on the shoe print. Various theories swirl, but Citizen and Jane narrow their focus to a security guard, Kevin Kowalski, who seems to be staring at Madeleine in multiple pictures they find on social media.

Citizen posts the photos they find of Kevin on the Real Crime Network. Shockingly, Kevin himself responds. He and his wife were in Disneyland that weekend, and he posts proof. The network explodes in criticism of Citizen and “The Newsline5,” as someone derisively labels Jane’s group. It is clear that there is still animosity toward them after their brush with fame.

Citizen shrugs off the abuse. His father was an angry, strict man who had an alcohol addiction and died of cirrhosis of the liver when he was 17. After the childhood he had, little rattles him. Jane feels even closer to Citizen knowing that they both lost their fathers. She spends an increasing amount of time online. Her job at Starbucks has become secondary.

A woman who uses the screen name “TiffyTracksKillers” and wears a revealing schoolgirl outfit in her videos finds security footage from the restaurant where Larissa dined on the night of the murders. She was with an older man whom Tiffy claims is one of her professors. She urges the public to look into both Chandler and the professor, arguing that one of them killed the women as part of a fight over Larissa. The internet goes wild. Mainstream media begins to report on various online sleuthing communities.

Jane combs through Reddit, finds two of Chandler’s frat brothers, and befriends them. They claim that he has an alibi for the time of the murders but doesn’t want to go public because he was seeing someone new and feels guilty about how much pain he caused Larissa. Jane urges them to change his mind: Otherwise, she argues, the harassment is not likely to stop.

Chandler eventually does make a statement, in which he also explains that he is dropping out of school because he’s gotten so many death threats. Shortly afterward, several strangers beat him badly. The professor also has an alibi, but the media and the public have begun to hound him, too. He resigns from his job, and his wife files for divorce.

Chief Reingold holds a press conference in which he blames the online sleuthing community for generating the harassment that resulted in Chandler’s beating. He posts old, unflattering photographs of Citizen, Goku, Mistress, Lightly, and Jane. He also mentions an old case in which Citizen created a media storm around an innocent man, cites Goku’s involvement in a violently misogynist group, mocks Mistress and Jane for believing that they are intelligent enough to solve crimes, and shows a mugshot from an incident during which Lightly assaulted a fellow officer.

The group is stunned and agrees that Reingold is lashing out in part because of the recent media storm surrounding him: He and his department have been maligned for their lack of progress in the case, and he resents the characterization of the department as “bumbling” and inept.

Reingold’s revelations about Goku and Citizen initially shock Jane, but as she speaks more with them, she understands their checkered pasts better. For Goku, the dubious community he found on 4Chan represented the only friends he’d ever had. He always struggled socially, and although he didn’t agree with his new friends’ ideas, he was happy to have a community.

Goku reveals that he and Citizen have been investigating the Delphine Police Department further on their own and that he himself was able to hack into its computers. He learned that Harlow hated her roommates; that she reported a stabbing (rather than a murder), so a rookie team was initially sent; and that her friend Jordan walked through the entire crime scene. The police department has a history of similarly botched cases, and Goku and Citizen want to make that information public.

The group argues over whether or not to release their new information. Lightly points out that publicizing the crime-scene issues could result in the murderer escaping justice: All evidence from the scene would become inadmissible. Things get heated, and the idea surfaces of just releasing information about Harlow, including her fraught history with her roommates and her strange claims that she didn’t hear the murder and wasn’t surprised to see a stranger in a ski mask walking through her home.

The group releases its new findings. Instantly, the tide of public opinion turns in favor of online sleuths, while various media outlets mock the Delphine Police Department’s ineptitude.

Madeleine’s parents go public: They deem the Delphine police incapable of solving the murders and ask for the online sleuthing community’s help. Citizen and Goku are thrilled, but Lightly is furious. He repeats his warnings about proper investigatory procedures and notes that the group might have given the killer’s future lawyer enough ammunition to get the case dismissed. He tells them that he is quitting.

Mistress tells Jane that the case that ended Lightly’s career was actually personal: The young victim was a family friend. She explains that he is a principled man who quit the force because he became disillusioned with policing and now feels that the amateur group has stopped centering the victims. Mistress is sure that to Lightly, it seems that the group is motivated by ego.

Taking a break from the case, Jane peruses a Star Trek forum that her father frequented. She learns from one of his friends that he wrote fanfiction. While she waits for them to find the piece, she pops back into the true-crime world. Many people have pointed out the discrepancies in Harlow’s story, and Jane decides to dig through her social media for clues.

In their first call without Lightly, the group argues over whether or not the killer could have been a woman. Jane and Mistress argue that Harlow could have killed her roommates, but the other two balk at the idea. They notice a new detail that they missed in the autopsy: Madeleine was stabbed more than 30 times and the other two fewer than 10, suggesting that Madeleine was the primary target. Their conversation is interrupted when they learn that the Delphine killer just struck again.

The new victims are also NIU students: Greta Danvers, Katya Novik, and Shuri Washington, all members of the women’s track team. The killer again used a knife and again entered their home through the sliding glass door. There is now a large media circus in Delphine as well as a growing community of online sleuths, including people who road-tripped to the small town and are now camped out in hopes of having better access to clues.

Lightly rejoins the chat. Everyone agrees that they are a “family” and that they can move beyond their argument. Lightly is particularly eager to return to the investigation because the murders are likely the work of a serial killer and now the responsibility of the FBI. Lightly has a friend on the investigative unit and will have insider information.

In the crime-scene photos, Jane notices an eyelash on the floor. Lightly tells them that he will pass this information on to his contact.

Jane is still interested in Harlow. She tracks down Harlow’s friend Jordan and asks if he’ll talk to her. Surprisingly, he messages back. He is a forensic-science major, and Harlow called him to her house after she found the bodies. She wanted to know if he could tell her anything about the killer. He got the sense that she either felt guilty for having let her roommates’ killer walk out of the house or was interested in “self-preservation.” Jane wonders why this information, which Jordan tells her the police know, was not included in their reports.

Hale, Lightly’s FBI friend, joins the chat. The FBI believes that the eyelash belongs to the killer. It matches the DNA profile of another unsolved killing, that of someone named Bridget Howell. He explains that he wants the group’s help: Law enforcement is barred from using sites like Ancestry.com, and he would like the group to see if they can upload the DNA to get a match. They will not be deputized or paid, but they are officially part of all three cases.

Bridget’s case is 12 years old, and there is little information about her online. Still, Jane does her best to scour the internet for clues. She enjoys getting lost down “rabbit holes” and is sure that if there is anything relevant about Bridget online, she’ll find it.

Jane misses so many shifts at Starbucks that she loses her job. She isn’t too bothered because she’d rather spend all her time digging into the Delphine murders, but Mistress and Goku warn her about obsession. Mistress tells her that she once nearly fell victim to a man who was later identified as a serial killer. After learning his identity, she became dangerously obsessed with finding his last victim; she was not successful, but she let all her other responsibilities go during the investigation. Jane appreciates Mistress’s concern but cannot tear herself away from her computer.

Late one night, Jane has a breakthrough in Bridget’s case. The police were almost sure that a random predator killed Bridget, though all the doors to her house were locked when she went missing. Looking at the photos of Bridget’s house, Jane notices a kind of lock that was recalled when she was in high school. It was marketed as additional security for homeowners—an external lock that could be attached to front doors and was unlocked with a numerical code. However, there was a hack: If someone pressed “0” seven times, the lock would open. Bridget’s killer could have used the hack to make it appear that no one had broken into her home.

The group decides to travel to Delphine to investigate the case in person.

Jane hears from her father’s online Star Trek friend: He has found her father’s fanfiction and sends Jane a link. She reads the piece, marveling at its complexity and nuance; her father was an excellent writer. She wonders how much of his personality she never had the chance to get to know and feels a new wave of grief settle over her.

Jane’s mother is livid when Jane explains her plans to fly to Idaho. They have a heated argument in which Jane accuses her mother of developing an exercise and health-food addiction. Jane’s mother tries to explain that she is attempting to come to terms with losing her husband, but Jane waves her off dismissively. Her mother accuses her of obsessing over true crime as a way to avoid grieving and points out that she looks terrible and has gained weight. She tries to forbid Jane from going, but Jane reminds her mother that she is 24 and can do what she likes. She boards a plane to Idaho.