As one burglar pockets a jeweled egg, another causes a noise that awakens the residents. When the man investigates, a burglar throws him off a staircase to his death.
Later at the Covington Youth Center, a girl hands the egg to another girl, who promises to not tell where she got it.
Meanwhile, Cal has Emily practice parallel parking, and she crashes into a hydrant. When they get home, Ria plays Cal a phone message from Ava, her delinquent half-sister, asking for help.
Cal, Ria, and Gillian go to Covington, where the deputy warden says Ava is in solitary confinement. Cal plays Ava's message. The warden explains that Ava's friend, Marley, ran away last night. Ria starts sobbing and threatens to take that message to the local news unless she sees Ava. OK.
Ria and Cal question Ava, who is hostile and manipulative. She denies knowing Marley's whereabouts. The staff psychologist, Dr. Burns, explains that Ava's dad was an alcoholic child-beater, her mother O.D.'d several years ago, and she's been in the system since. Meanwhile, Marley has been found dead from a hammer blow to the head.
Ria informs Ava, who remains uncooperative. Cal, who notes that Ava plays on Ria's guilt for being unable to protect her from their father, says they'll leave if she doesn't talk. Ava says Marley was pregnant -- Ava doesn't know who's the father -- and last night she heard Marley scream for help but ran away instead.
Cal, Gillian, and Ben confront the deputy warden, who denies knowing Marley was pregnant. But Burns did, adding Marley was disciplined for making out with Tyrell in chapel months back. But the deputy warden says Tyrell was released last month. Cal wants to see the group therapy tapes. Burns says those are confidential, however the deputy warden agrees to show them Marley's last session.
While Ria and Ava go to her room -- which Ava discovers has been searched, but the egg is still there -- Cal watches the tape. One boy, Maurice, is noticeably hostile, so they search his room and find a bloody hammer. Maurice denies killing Marley. Ria knows he's not lying.
That night, Cal helps Ava escape from Covington, puts her up at Gillian's, and orders Ria off the case. Then he interrogates Burns, whom he accuses of impregnating Marley. Burns didn't. His guilt comes from not reporting her pregnancy; she'd have been transferred and not dead.
Cal goes home and finds Ria, drunk. After throwing Ria into a cold shower, Cal says their father taught Ava how to lie and Ria how to see the truth. Ria replies Ava is manipulative and doesn't care who she hurts, just like Cal.
Meanwhile, four masked marauders break into Gillian's home, tie her up, and take the egg from Ava. When Ria accuses Ava of being complicit in the robbery, Gillian disagrees, noting the intruders -- three men and a woman, she could tell from their voices -- took the egg from Ava, who's disappeared.
A young man named Dax, who works for the deputy warden, delivers the rest of the therapy tapes to the office, adding, "You didn't get them from me," and leaves. When Gillian and Eli review the tapes, she recognizes a girl's voice as being that of one of her assailants.
As Cal and Ria stake out a house that Ria says Ava always goes to, Cal says Ria needs to believe Ava. Then they see Ava get into Tyrell's car and put on a mask.
Back at the office, Gillian interrogates the girl, Amber, as Burns and Eli watch. Burns is impressed. Amber confesses to being part of a crew of Covington inmates that committed robberies for reduced sentences. Burns doesn't believe her, saying the deputy warden signs off on those releases.
Ben brings in Ava, and Ria confronts her about the mask. Ava says she just wanted to know what it felt like to have power over people and she was holding the egg to help Marley. Ria asks Ava to trust her.
Tyrell tells Cal that several months ago, they did a robbery "and serious stuff went down." He kept the egg for leverage, then gave it to Marley so she could get early release because she was pregnant. Ava didn't talk because she'd promised Marley she wouldn't.
When Cal puts the deputy warden in the cube, she claims Dax forced her to sign the early releases by threatening her parents, and he killed Marley. But Dax, who admits killing the man during the robbery, claims the warden wouldn't let him stop and that she killed Marley.
But Cal produces her fat bank accounts (under false names) and shows her all the kids from Covington are watching this interrogation. Ria says when Marley showed her the egg, which would've exposed the robbery ring, the warden killed her.
Ria adds they've recorded this interrogation, so it's not the deputy warden's word against Dax's. "It's your word against mine," says Cal. "You lose." The kids applaud, and the deputy warden is handcuffed.
Cal tells Ria that Gillian will get Ava into a friend's boarding school, but Ria wants custody. Cal says she has to let Ava find her own way. When Eli and Ria drop off Ava at the school, the half-sisters exchange teary goodbyes and hugs.
Meanwhile, Burns comes to the office with flowers for Gillian, who smiles. And Cal watches Emily pass her driving test.