Piper struggles to adapt to life after Litchfield. Now living with Cal and Neri, she is unable to pay her rent and probationary fees. She confronts her wealthy father, who is unwilling to support her financially. Alex attempts to get rid of Badison by planting a phone in Badison's dorm. However, Taystee finds the phone instead, which results in a violent confrontation that sends both her and Badison to the SHU. CO Hellman forces Alex to deal heroin until Badison returns. Aleida's kids have moved in at Hopper's residence. Lorna has given birth to a baby boy, Sterling. Daddy's infidelity angers Daya, who accidentally kills Daddy with an overdose of fentanyl as revenge.

Maritza, released on parole, connects with an NBA player whom she met at a club. Piper earns her keep by babysitting. Linda fires Figueroa from her interim warden position; Aleida pressures Hopper to try out for the warden position. Tamika wants to be promoted to head guard, and asks Caputo for advice. Though Linda had initially planned to hire Hopper, Linda is impressed with Tamika and hires her as the new warden. McCullough catches Alex trying to get rid of Hellman's drugs. Realizing that reporting Alex and Hellman for the drugs will do nothing, McCullough instead forces Alex to sell the heroin for her. Daya is determined to usurp Daddy's position in prison. Maritza is arrested during an ICE raid and is sent to the PolyCon detention facility.

Tamika begins her term as warden. Though Tamika is disheartened to learn she had only been hired for being black, she is inspired by Figueroa's advice to do whatever she wants. Tamika closes the SHU and transfers Badison to a Missouri prison. Maritza fails to prove her American citizenship. She also reunites with Blanca at the facility. Diablo visits Blanca, but he is taken into custody due to his expired green card. Suzanne tries to mend Taystee and Cindy's relationship, to no avail. Alex flushes Hellman's heroin down the toilet, and convinces McCullough to smuggle portable phone chargers instead. Piper begins working for her father's company. Red, Gloria, Nicky, Lorna, and Flaca are assigned to run the kitchen at the PolyCon facility where Maritza and Blanca are staying.

Piper grapples with her new job. Maritza reunites with Flaca, who is able to contact Maritza's estranged mother. However, Flaca is told that Maritza was born in Colombia and does not have a U.S. birth certificate. Tamika creates new prison education programs; Maria and Cindy find solace in Caputo's restorative justice class, while Pennsatucky takes part in a GED course. Lorna finds out from her husband that Sterling had tragically died from pneumonia; Lorna refuses to accept Sterling's death and maintains the belief that her child is still alive. A suicidal Taystee tries to buy fentanyl from Daya, who has become the prison's kingpin. Daya refuses to make the offer. Taystee later attempts to hang herself, but she backs out at the last second.

Aleida is arrested when she beats up her daughter's drug dealer boyfriend. Piper and Cal shed their responsibilities for a day by drinking alcohol and getting high. When Piper is caught tampering with her drug test, she is ordered by her parole officer to attend Narcotics Anonymous meetings. Red starts to become forgetful. Taystee begins working as Tamika's assistant. However, Taystee plans to take advantage of her job by providing outside information to Daya, in hopes she will eventually get the drugs she had asked for. Cindy is up for early release. Blanca is able to extend her court date. Gloria gives Maritza a free number that can help her contact a lawyer, but when Maritza gives the number to other detainees, she is caught by the guards and deported to Colombia.

Maria is shocked when Yadriel reveals that he and their daughter are moving in with his new girlfriend. Maria is initially enraged but, inspired by Caputo's assignment to reflect on who she has hurt, apologizes to Yadriel for not trusting how he's raising their daughter. Cindy, also inspired by Caputo's assignment, apologizes to her mother as her release date impends. Taystee exacts revenge on Cindy by writing a letter to Cindy's daughter, Monica, that reveals Cindy as her real mother. Alex and McCullough continue their smuggling operation. Linda closes down the psych ward. Caputo discovers that Susan Fischer, the female CO unfairly fired by Caputo in the second season, is accusing him of sexual harassment. Cindy is released from prison.

Nicky finds romance with Shani, one of the ICE detainees. Blanca bonds with Karla, who shows her an online legal library she can use to prepare her case. A lonely Piper follows Alex's advice to have sex with another person, though this only makes Piper want Alex more. McCullough kisses Alex. Pennsatucky fails her GED practice test; her teacher determines she may have dyslexia, and recommends Pennsatucky get a tutor. Caputo tries to apologize to Fischer. Daya sends Taystee on a mission to retrieve her phone taken during a sweep. Nicky finds Red, delirious, sitting in a freezer. Suzanne gives a journal to Taystee explaining what had happened the night Piscatella died. Tamika finds the journal and encourages Taystee to give this new information to her lawyer.

After Tamika allots PolyCon's money towards the inmates' programs, a furious Linda prohibits her from extending the prison budget. Now unable to hire GED tutors, Tamika convinces Taystee to tutor Pennsatucky. Daya gives Taystee the fentanyl; Taystee hides the baggie behind a poster in Tamika's office. Aleida returns to prison and has a fiery reunion with Daya. Aleida cuts out Daya from her drug operation. Suzanne tends to the prison's new chicken coop. Nicky confronts Red about her worrying signs of dementia, but Red remains in denial of her condition. McCullough and Alex begin a sexual relationship. Neri takes Piper on a wilderness retreat. Piper bonds with a group member, Zelda. She confides to Zelda over her time in prison and her inability to adjust to the outside world.

Cindy's family breaks apart when Monica receives Taystee's letter. Though Cindy's mother, Lillian, advises her to make amends with Monica, Cindy decides to run away instead; Lillian orders her never to return. After being cut out by Aleida, Daya threatens the prison's GED teacher into becoming her new drug mule, which prompts the teacher to resign. Karla's request to attend her children's custody hearing is denied. Shani confides in Nicky about her traumatic childhood. Piper comes out as a felon to her co-workers. She also makes amends with her father. Fischer gets a restraining order against Caputo. Vince leaves Lorna over her inability to accept Sterling's death. A distraught Lorna attempts to leave the prison, putting the building into lockdown.

Lorna is found in the chicken coop and subsequently sent to medical. McCullough is left visibly shaken by the lockdown, and she is comforted by Alex. The lockdown also has consequences for Tamika, who is put on notice by Linda. When Red accidentally cuts herself in the kitchen, the doctor diagnoses her with early onset dementia. Shani finds out she is being deported. Maria apologizes to CO Dixon for her involvement in the riot. Caputo owns up to his misdeeds and informs Tamika of his resignation. Luschek takes over as the new teacher of the GED course. Piper decides to reconnect with Larry and Polly, and Zelda joins along; Piper and Zelda continue to flirt. Alex finds Zelda's social media and discovers her and Piper's relationship. A frustrated Alex continues her sexual relationship with McCullough.

Zelda invites Piper to a posh fundraiser and admits she wants to start a relationship with her. Alex feels guilty about her infidelity, and she breaks up with McCullough. A heartbroken McCullough confronts Piper at her house and states that Alex needs to move on. Piper has sex with Zelda. Maria tries to make peace with Gloria. Nicky attempts to stop Lorna's transfer to Florida. Nicky consults with Vince and learns of Sterling's death. Aleida tips off the guards about Daya's hiding spots. Shani leaves a goodbye note for Nicky before she is deported. Figueroa is sympathetic towards Santos, a pregnant ICE detainee who was raped while trying to enter the United States. When Santos tries to naturally induce a miscarriage, Figueroa secretly smuggles in abortion pills for Santos. At her appeal, Blanca is able to buy more time by reopening her criminal case. Karla, however, is deported to El Salvador. Karla calls her kids with an emotional message through Gloria's illegal phone—the phone is later found by CO Bell.

The guards begin interrogations over the illegal phone. Despite her release date approaching, Gloria confesses to owning the phone. Taystee consults with her lawyer and discovers that Suzanne's journal cannot be used as evidence for a trial. Discouraged by this news, Taystee plans to commit suicide with Daya's fentanyl. Nicky reluctantly lets Lorna get transferred to the Florida block. Hopper is fired after getting caught having sex with Aleida. McCullough informs Alex that Piper is seeing someone else. Alex confronts Piper in visitation; Alex confesses that she doesn't have any feelings for McCullough, but Piper admits she has feelings for Zelda. McCullough has Alex transferred to an Ohio prison. During the GED exam, Luschek fails to provide Pennsatucky extra time for her dyslexia. Believing she had flunked the test, Pennsatucky snorts fentanyl from Daya's crew and overdoses. Taystee later discovers Pennsatucky's unconscious body and cries for help.

Pennsatucky dies from her overdose. Taystee discovers Pennsatucky had passed her GED exam. Suzanne, having been Pennsatucky's roommate, sets up a memorial for her in the Florida block. Zelda invites Piper to join her on a trip to Northampton. Piper visits Alex and is told of Alex's transfer; Alex thinks they should break up, believing she is keeping Piper from new experiences. A conflicted Piper confides to Larry, who advises her to "do what new Piper would do." Luschek takes the fall for Gloria and claims he had smuggled in the cell phones, resulting in his termination. Taystee returns her baggie of fentanyl to Daya. Upon discovering that Daya had brought her younger siblings into the drug operation, Aleida angrily chokes Daya. A homeless Cindy makes amends with Lillian and Monica. Red is transferred to Florida and reunites with Lorna and Frieda, but Red does not remember who Frieda is. Caputo and Figueroa visit an adoption clinic. In El Salvador, Karla follows a smuggler in an effort to get back into the United States, but breaks her ankle and is left stranded in the desert. When a bottle of Hellman's drugs are found outside the prison, Linda fires Tamika on the spot. Hellman replaces Tamika as the new warden.