South Central Los Angeles -- The naked, dumped body of an unidentified woman, dead of strangulation, lies in an alley. Neighborhood kids, desensitized to violence and death in their neighborhood, throw rocks at the body and videotape themselves doing it. Narrator: "Dead unidentified females in Los Angeles are often called a 'Sally in the Alley.' Our detectives wanted to give this one a name."
Dets. Nate Moretta and [name] are en route to the murder scene. Nate asks when he's going to get Tammi pregnant. [name] says they're nowhere near ready. Sammy ignores a call from Tammi, who wants a $2000 top-of-the-line Hasselblad camera. However, he admits her photography is really good. Nate's dad, frantic, calls him to say his 15-year-old sister Mercedes is missing. Nate tells Sammy that she's been hanging out with the wrong crowd for the last few weeks. At the murder scene, Kenny No-Gun updates them about the kids and unintentionally impresses everyone with his encyclopedic knowledge of the chemical properties of ropes and fishing line.
Lydia awkwardly manages conversation on a blind date over brunch. Her date, Talib, wonders if he's passed the test to take her out on a real dinner date. When he asks what she does for a living, she vaguely says, "A community advocate." In the middle of their meal, she gets called away. She apologizes on her way out. When he asks, she tells him he can call her again, but it's clear she doesn't care either way. Det. Russell sits in his writing class, taught by Keren, whom he met during her sister's murder investigation. His phone vibrates -- it's Lydia calling him into work, but he turns it off.
Nate and Sammy show vice detectives Eddie and Shauna a picture of the murdered woman. They've seen her and think her street name is Cherry. They agree to show the photos around. At the office, Lydia chastises Russell for turning off his phone when he's on call. She tells him to get his ass in the office, as Gaines needs their help on a homicide. At the morgue, Lydia becomes frustrated when an overworked, unsympathetic pathologist won't fingerprint the victim's body right away. When she tells him that they had trouble with the fingerprint scanner at the scene, he says that's not his problem and walks off.
Mrs. Miller, a visitor so frequent that they've dubbed her "Miller Time," comes to the office to make yet another police report. It's Nate's turn to take the report. She says her daughter Princess is missing -- since January 7, 1992. Nate pretends to be writing the information down in his pad, but he's only drawing a frowny face. Kenny calls him over and shows him the video of the kids throwing rocks at the body -- it's been posted on You Tube. Nate notices a cross necklace on the victim that wasn't there when they arrived on scene.
Nate finds the kid who took the necklace and hauls him into the station. Unashamedly wearing the murder victim's necklace, he puts on a tough act, even when they say they'll book him for murder. However, when Sammy asks him where he got the cross, his cockiness fades. Tammi visits the station and interrupts to tell Sammy a woman offered to pay her $200 for Richter, their retired police dog, to search their son's room for drugs. She's so excited about the prospect of earning enough money to buy the Hasselblad that she wants to advertise the service. Sammy expressly forbids it. When she starts to argue, he reminds her that he's working.
Meanwhile, Lydia and Russell check in with the vice cops and learn they haven't found anyone who recognizes the murder victim. Russell is willing to wait until the prints come back, but Lydia won't settle for that. They drop by a women's shelter and Lydia hits pay dirt. A regular recognizes her as Nicole Johnson. Meanwhile, Sammy and Nate work the kid and get him to admit that he took the cross, but didn't murder the girl. The boy says he saw some old white dude in a white van with curtains on it circle the block a few times before dumping the body.
While Lydia searches Nicole's records, Russell's on the phone with Karen discussing her class. Detective III Alicia Fernandez, orders them to drop everything for a shooting on Hollywood and Highland. When Lydia protests, Alicia quips, "You know what? She'll still be dead in five hours." When they arrive on scene, Lydia notes that there are more cops there than were in the North Hollywood bank shootout. She learns from Antonio, a reporter who's equally incredulous at the overkill response, that a tourist was shot in the leg while fighting off a robbery. Lydia seethes when she sees Cathleen Kerik, head of LAPD media relations, talking to reporters.
Despite Sammy's objections, Tammi goes to the couple's house and sets Richter loose in the boy's room. Richter grabs a shoe and won't let go of it even when Tammi commands him to do so. The boy comes home and sees his Air Jordans being ripped to shreds and runs at them. Richter sinks his teeth into the kid's arm and won't let go. The kid pulls away, with a bloodied arm. Tammi gets the shoe free, then pulls out a baggie of drugs from it. She shows it to the family and says, "This is why he was acting so crazy."
At home, Sammy waits while Nate talks to his father about Mercedes, who still hasn't returned. His father gives him the name of the boy she's hanging out with, Edwin, along with his phone number. Nate is disturbed to learn he's 18. He calls Edwin, who only smart talks him. He asks Sammy to trace the address through the phone number. Meanwhile, Lydia, anxious to get back to her murder case, smarts off to Cathleen in front of the press, "Are we done here, or are we waiting for the National Guard?"
As Nate and Sammy wait outside Edwin's house, Tammi calls Sammy about the dog incident. Furious, he curses her out, worried that they can be sued. Lydia and Russell visit Nicole's mother, who is caring for Corbin, her daughter's son. Russell gets the task of telling Corbin, who's already guessed. When Russell expresses his condolences, the boy matter of factly states, "She was a whore." Russell says she was his mom, and that while he'll always remember this night, he can still build good memories about her, focusing on the nice things. He gives Corbin his card and tells him to call to talk, anytime.
Lydia brings the rape kit to forensics and asks for a rush on it. She's incredulous to learn that they have a backlog of 3000 cases. She notices that a batch of them are ten years old. When she raises a stink about the backlog, the forensics doctor, who has two daughters himself, is sympathetic but says they were promised funding to outsource it but it never came through. On their way out, her date calls, and she says it's not a good time to talk. Russell teases her about no man being able to get a second chance.
At home, Dina accuses Russell of competing with her when he says he wants to write. When he becomes defensive, she accuses him of screwing the teacher. Lydia arrives home to an expensive flower arrangement, compliments of Talib. Her mother, cooking dinner, compliments his taste. Sammy gets home to a contrite Tammi, who turns his rage into a passionate lovemaking session. Nate tells Mariella, his pregnant wife, about Mercedes. She assures him that he's not in this alone.
The next day, Lydia is called into Alicia's office to apologize to Cathleen for her behavior. Lydia admits she was frustrated for being pulled off her case, then asks why no one's doing anything about the backlog of rape kits which hasn't garnered a single article. Alicia tries to reel her in, but Lydia's on fire. Cathleen asks Lydia what it is she doesn't like about her. Lydia doesn't hold back, and lists everything from the fact that if the girl was found in a Brentwood alley, it would be front page news.
Having heard about Lydia's murder case, Mrs. Miller speaks to her about her own daughter's case, which she says is just like this one. Instead of treating her like a nuisance, Lydia takes her to an interview room. On day two of his mission to find Mercedes, Sammy asks him what's really going on. Nate reveals that Mercedes isn't his sister, but his daughter that he fathered as a teenager. His parents raised her as his own, and Nate thinks she may be acting out because she found out the truth.
Lydia's day improves when she finds that the forensics doctor got a hit off the fingernail scrapings. She's surprised that he did that for them. Russell says he did it for her, noting that he'd want her on the case if his girls ever needed a detective. The DNA led back to Lester Brown, a registered sex offender.
Nate and Sammy storm Edwin's house during a party, navigating through a bunch of gang bangers until they see Mercedes. She tries to run, but Nate catches her. As he marches her to his car, she screams at him, furious at having learned he was her father when she needed her birth certificate for a driving test.
Lydia and Russell, along with the sheriff's department, approach Lester's house in Palmdale, guns drawn. An old white van sits in his driveway. They knock on the door; Lester sees them and runs for it. The canine officer releases the dog, which clamps onto his arm and wrestles him to the ground. Lydia catches up and cuffs him, getting to say these extremely satisfying words, "Lester Brown? You're under arrest for murder."
Lydia meets with Antonio to discuss her theory that Lester Brown is a serial killer. She gives him Princess' case file, noting the similarities in both cases. A white van twenty years ago. A white van now. Both victims were prostitutes, working in Hollywood. She says that Lester admitted dumping Nicole in South Central because he thought no one would notice. Antonio agrees it's a good story. Lydia says the article could help her re-open Princess's case. She asks about his progress on the rape kit backlog article. He assures her he's working on it; it's a huge story that makes everyone look bad. She tells him, "Work faster."
Nate tells Mercedes why he lied and is sorry she found out this way. He hasn't seen her mother, who fell into a bad crowd, but he promises to help find her. Sammy maxes out three credit cards to buy Tammi her Hasselblad. Lydia shows Mrs. Miller Antonio's article about Princess, saying the publicity will help her reopen her case. Mrs. Miller is in disbelief that someone is finally championing her daughter's case. Russell gives Corbin his mother's cross. He asks Russell if it's good that they caught the guy. "Definitely," Russell says. Later, Lydia lets Talib take her out for dinner and reveals she's a cop. He's surprised. She says she loves her job, adding, "I had a good week."