Porter and Nash emerge from the Mulifax Publications Building after spending three hours processing the kill room. Porter orders Espinosa’s team to search the Moorings development. Clair argues with Captain Dalton by phone, and Nash correctly guesses Dalton is refusing to authorize bringing Talbot in for questioning. Porter reflects that the Four Monkey Killer always targets families for specific illegal activities, making Talbot’s involvement certain. He worries about Emory Connors, missing over a day without food or water.

Clair relays Dalton’s orders: additional patrol cars will search both sites, the detectives must rest, and they cannot officially interview Talbot until they have complete financial records, a strategic move. Clair reveals Talbot owns the Mulifax Building. He assigns Clair to supervise the Moorings search and Nash to supervise Mulifax, and he decides to surveil Talbot’s house himself. Porter gives Nash a fingerprint lift from a railcar in the sub-basement to deliver to the lab.

After the diary narrator enters to stage the Carter house, he hears clanking from a bedroom down the hall. Believing a trespasser is inside, he draws his knife and rushes into the room to attack. The intruder is his mother, who easily disarms him and criticizes his technique. Mother keeps his knife, saying he must earn it back. While packing random clothing and toiletries to create a confusing narrative, the diary narrator finds a photograph inside a book on the nightstand. The image shows his mother and Mrs. Carter naked and kissing in the Carters’ bed. He realizes their affair predates yesterday and wonders who took the picture. Mother snatches the photo and warns him not to tell his father.

After surveilling Talbot’s house all night with no developments, Porter returns to his apartment at dawn. He finds the building’s secure entrance propped open and dog excrement on the steps, courtesy of his neighbor, Carmine Luppo, a disabled former bathtub salesman. Porter collects his mail, keeping only a TV guide. He enters his apartment carrying cold fast food. On the bed lies the note his wife Heather left saying she went to get milk, which he hasn’t moved since she was killed. He calls her voicemail and leaves a message about needing to find Emory Connors before beginning to cry.

The diary narrator waits outside with a baseball, keeping up appearances while trying not to think about the photograph of his mother and Mrs. Carter. His father arrives home. To dispose of the Carters’ car, Father leads in his Porsche while Mother follows in their vehicle. After his parents leave, the diary narrator hears banging from the basement. He finds Mrs. Carter, still handcuffed to the water pipe, swinging the cot against the pipe in an attempt to break it. He points out the flaw in her plan: If she ruptures the pipe, the basement will flood and she will drown while chained. Mrs. Carter pleads to be freed, promising silence, but he refuses. When he wipes a tear from her cheek, he tells her he found the photograph. Mrs. Carter panics, asking if his father has seen it. She warns that if Father discovers the photo, he will harm both her and Mother.

Porter arrives at the team room, where Nash, Clair, and Watson are examining a laptop. Watson shows Porter a clay facial reconstruction of the Four Monkey Killer. Porter instructs Clair to circulate the image at cancer treatment centers. Clair reports the Mulifax Building victim has been identified as Gunther Herbert, chief financial officer of Talbot Enterprises. Fingerprints lifted from the shoes the Four Monkey Killer wore match Arthur Talbot. Watson explains he cannot retrieve the pocket watch found on the Four Monkey Killer from evidence without Porter or Nash present.

Captain Dalton arrives and privately informs Porter that police at the Fifty-First Precinct arrested a suspect in an attempted robbery. The suspect’s weapon is a ballistic match for the gun that killed Heather. Dalton allows Porter to observe the lineup but orders him to leave his personal firearm behind. Clair reports that financial investigator Hosman has a lead on Talbot’s finances. Porter tells Clair and Nash he is taking Watson to the Fifty-First Precinct.

The diary narrator pretends to sleep and overhears his parents return, arguing in the driveway. Inside, Mother refuses to participate in Father’s plans and slams her bedroom door. Father, masking his anger with forced cheer, wakes the narrator and asks for help with a surprise for Mrs. Carter. He tells the diary narrator to bring Mother’s large salad bowl from the kitchen and meet him in the basement. Father reveals a paper sack containing something that scratches and moves inside.

Clair and Nash meet with financial investigator Hosman, who explains Arthur Talbot is running a Ponzi-like scheme, shuffling investor money between projects. Hosman details how the city’s Historical Preservation Division blocked Talbot’s Moorings development. When the city discovered Talbot used substandard concrete in two major downtown construction projects, they halted work on both. Talbot then sent a $4 million bribe to a city official. Shortly after, construction resumed at all sites. Talbot is now financially overextended, owing massive debts while using money from new investors to pay off old ones. However, the real fraud is at the Moorings: Talbot is selling development rights to land in phase two that he does not own. Hosman reveals the land legally belongs to Emory Connors, willed to her by her mother. Hosman shows them a legal document that prompts Nash to suggest they can finally bring Talbot in for questioning.

The diary narrator descends to the basement carrying the salad bowl and water. His father has gagged and completely restrained Mrs. Carter to the cot. Mother had silently urged the diary narrator not to participate, but he ignored her. Following orders, the diary narrator cuts off Mrs. Carter’s blouse. Father places a paper sack containing a drugged field rat on her exposed stomach, then covers it with the plastic salad bowl, taping it securely to her skin. He removes the gag and demands to know if Mr. Carter was having an affair with his wife. Mrs. Carter denies it. The rat awakens and begins biting and scratching her abdomen as she screams. Father spills water near the bowl’s edge, agitating the thirsty rat further. He threatens to skin her fingers if she lies. She passes out. Father orders the diary narrator to untie the ropes but leave the handcuffs, then goes upstairs to confront Mother.

Emory awakens pinned beneath the hospital gurney that collapsed on her. Her wrist is badly broken and severely swollen around the handcuff. Despite intense pain, she manages to stand using the gurney for support. She has wet herself. Rod Stewart’s “Maggie May” plays from above. Emory hallucinates a conversation with her deceased mother’s voice, which taunts her about her predicament as she wonders how much longer she can survive.

After tending to Mrs. Carter’s wounds in the basement, the diary narrator goes upstairs and finds his father unconscious on the couch, an empty bourbon bottle beside him. In his bedroom, Mother confronts him holding a large butcher knife. He confirms Mrs. Carter did not reveal their affair to Father. Mother threatens to murder him in his sleep if he tells Father about the photograph. She first tries bribing him with sexual access to Mrs. Carter, then threatens to claim he is a “pervert” who spied on them. The diary narrator demands to know who took the photograph, suggesting it was Mr. Carter, which would support Father’s suspicions of an affair. Enraged, Mother lunges with the knife, then stops, drops the blade, and storms out. The diary narrator takes the knife, barricades his bedroom door and windows, and prepares to sleep in his closet for safety, clutching the weapon.

In the car en route to the Fifty-First Precinct, Porter tells Watson the complete story of Heather’s death. She went to a nearby market late at night for milk while he slept. A nervous robber entered and, startled by her presence, accidentally shot her. Porter expresses profound guilt for not stopping for milk earlier that evening. Watson, who has a psychology degree, listens and tells Porter that talking is necessary for healing. Porter drives erratically, unsettling Watson. At the station, Porter takes the pocket watch from Watson and stashes his gun under the car seat before entering, as he is technically still on leave and not authorized to carry.

The diary narrator is home alone when a heavyset elderly man in a trench coat knocks. The man displays a badge and says he is looking for the Carters because Mr. Carter missed work. The diary narrator repeats his story that the Carters are on a trip. The man points out that the Carters’ mail and newspapers are accumulating and asks if the diary narrator can let him into the Carter house. The diary narrator, suspicious, challenges the man to show his badge again. The man declines, backs down, and says he will return when the diary narrator’s parents are home. Before departing, he warns the diary narrator about being home alone, which the diary narrator perceives as a veiled threat.

Clair and Nash interrogate Arthur Talbot with attorney Louis Fischman present. They confront him with multiple pieces of evidence: his CFO Gunther Herbert’s murder, his ownership of the Mulifax Building, his dire financial situation, and the fact he is fraudulently selling land owned by Emory. Talbot offers plausible explanations for each point. Critically, according to Emory’s trust, if she dies before turning 18, the land reverts to the city, not to him. This proves he needs her alive. When confronted with his fingerprints on the shoes the Four Monkey Killer wore, Talbot claims they were stolen. After the interview, Nash argues the Four Monkey Killer is using Talbot as his target and they should not develop tunnel vision. Detective Belkin calls with a breakthrough: a nurse at a medical center identified the facial reconstruction. The suspect is Jacob Kittner, a cancer patient who wore a fedora and stared at a pocket watch during treatments. Clair orders a SWAT team to Kittner’s address.

The diary narrator, Mother, and Father eat dinner in tense silence. The diary narrator tells them about the man searching for the Carters. When he mentions the visitor drove a green Plymouth Duster, Mother has a visible reaction. Father questions her, but she denies knowing the man or the vehicle. Both the diary narrator and Father perceive she is lying.

Porter and Watson meet Detective Ronald Baumhardt at the Fifty-First Precinct. Baumhardt explains the suspect, Harnell Campbell, was arrested during an attempted 7-Eleven robbery and subdued by an off-duty officer using a can of beer. Tareq, the cashier from the night Heather was killed, arrives to view the lineup. He immediately identifies number four, Campbell, as the shooter, noting a specific tattoo on his ear reading “Filter” that he had described to investigators. Porter is visibly shaken by seeing his wife’s killer and tells Watson he needs to leave before the interrogation begins. He cannot trust himself to remain objective. As they exit, Porter collides with another detective, spilling hot coffee onto both their clothes. Porter tells Watson they need to stop at his apartment so he can change.

Clair and Nash join Espinosa’s SWAT team at Jacob Kittner’s apartment, a hoarder’s dwelling with newspapers and books stacked floor to ceiling throughout the living room. They find a cat but no sign of Kittner or Emory. Financial investigator Kloz calls with updates: Kittner received two large wire transfers from a Cayman Islands bank totaling $500,000, with the second payment arriving after his death. Kloz reveals Kittner’s deceased sister was Amelia Mathers. Emory’s boyfriend is Tyler Mathers, making him Kittner’s nephew. Espinosa emerges from the bedroom holding Emory’s cell phone with its battery removed. Clair and Nash decide to immediately bring Tyler Mathers in for questioning.

After checking on the lake disposal site, the diary narrator returns to find the green Plymouth Duster parked outside the Carter house again, keys in the ignition and engine warm. He sneaks into the unlocked passenger side and opens the glove box, finding a large revolver. He unloads the weapon, pockets the bullets, and returns the useless gun to the glove box. As he listens at the Carter house window, the man from yesterday, Mr. Jones, surprises him from behind. His wiry associate, Mr. Smith, is inside. The diary narrator’s parents arrive and approach. Mr. Jones and Mr. Smith claim to be Mr. Carter’s coworkers searching for sensitive work documents stored in a metal box. Mr. Smith found the box under the Carters’ bed, but it was empty. Mother firmly orders them to leave. The two men depart without resistance.

Emory shivers uncontrollably, her broken wrist grotesquely swollen. She hallucinates conversations with her dead mother’s voice, which confuses her by mentioning uncles with names she does not recognize—Roger, Robert, Steve, Ryan. Her mind is foggy from severe dehydration, making simple thoughts and calculations impossible. She takes her pulse and discovers her resting heart rate has climbed above 100 beats per minute, indicating dangerous physiological stress. She is so dehydrated she can no longer cry. The voice in her head taunts her about her impending death. Loud music continues from above as Jimi Hendrix plays.