A nun checks on Grace at the infirmary and discovers that she's hemorrhaging from her recent sterilization procedure. She refuses to call Arden, calling him a butcher, and tries to revive the dying Grace. Meanwhile, only Grace sees an old woman in black, the Dark Angel, appear in the infirmary and approach her. As black wings sprout from the woman's back, she kneels to kiss Grace. However, the nun administers CPR, bringing Grace back, and she says that they should have let her go.
Arden is tending plants in his office when Mary Eunice comes to see him. She tells him that Grace is bleeding out because Arden botched the operation but he insists that he didn't do any such operation. The nun jokingly says that he's joking and Arden tells her to respect him. When she informs him that he's not really in charge, Arden slaps her and Mary Eunice warns him not to it again. When he tries a second time, Mary Eunice throws him across the room with a gesture and tells him that now he should understand the chain of command.
One of the patients, Miles, is working in the kitchen when a voice in his head tells him that it's finally his time to do something important with his life. He screams at the voice to shut up and then explains to the sister in charge that he was yelling at the voice in his head. It persist, telling him to leave a legacy, and Miles picks up one of the prepared sandwiches and tells the sister that the slice isn't cutting properly. He then pulls up his sleeves and lowers his wrist onto the spinning slicer blade.
As the staff tend to Miles, Frank calls Mary Eunice in. She's shocked to see a name in an unknown language written on the wall in Miles' blood. When Frank wonders what it is, Mary Eunice says that it's in ancient Aramaic and asks Miles how he knew the name. He doesn't remember drawing it there and doesn't recognize it, but Mary Eunice demands to know if he summoned the Dark Angel. When he doesn't answer, Mary Eunice has the orderlies stitch up Miles' injuries and confine him to isolation, and then tells the staff to scrub the walls.
As Frank makes sure that Miles is strapped to a bed, Miles says that he doesn't want to live anymore. The head guard assures him that he'll feel better in the morning. The Dark Angel comes in response to Miles' request and says that she can help him if he wants. He pulls out the stitches in his wrist and begs the Dark Angel to help, and she agrees to kiss him and make it all go away. She bends over and kisses the patient, who bleeds out and dies.
Mary Eunice enters the room and sees the Dark Angel. It asks who dares to look upon Shachath and Mary Eunice tells her to leave now that she has done what she came to do. The Dark Angel realizes that Mary Eunice is more than she appears and recognizes the demon within as a dark cousin. She says that she was invited and that the real Mary Eunice trapped within her own body called to her. The real Mary Eunice manages to free herself long enough to speak, begging the Dark Angel for help, but the demon reasserts control, insisting that it and its host both like being in Briarcliff and still have work to do. The Dark Angel promises that they will meet again as she goes about her work and disappears.
Arden examines Grace and confirms that she's in critical condition. Disgusted, he tells her that he will have to treat her infection so that everyone knows that he wasn't to blame, and gives her an injection.
In Thredson's basement, the psychiatrist rapes Lana repeatedly. Emotionally numb, she looks over and sees the Dark Angel in the room.
At the police station, Kit tries to tell the detective that Thredson tricked him into making the conviction. The detective warns that no one will believe Kit's claim that Alma is alive, or accept Grace the mental patient as a witness that the dead woman isn't dead. He tells Kit that in any case, they've received word that Grace is dying. A desperate Kit snatches up a three-hole punch, knocks the detective out, and escapes.
Once Thredson goes upstairs, the Dark Angel approaches Lana and says that she heard the reporter calling to her. Lana says that death would be better for her and the Dark Angel bends over to kiss her. However, Lana shoves her away and says that she's not ready yet. As the Dark Angel fades into the darkness, Thredson comes down and says that he doesn't blame Lana, but he thinks that they've reached an impasse. He now has no choice but to kill her.
Lana breaks into tears and Thredson prepares to inject her with a sedative to make it as painless as possible. He shoves her onto the bed and tells her that she'll soon be with Wendy. Furious, Lana grabs the photo frame of her lover and smashes it into Thredson's head, knocking him to the floor. She then chokes him with her leg chain until he passes out, grabs the keys from his pocket, and runs for the stairs. Thredson tries to grab her but Lana kicks him back into the basement and runs out of the house.
As Lana runs down the road, a car comes by and brakes just before hitting her. Lana gets in and asks the driver to leave. He begrudgingly does so but as they continue on, he figures that Lana attacked her boyfriend. When she asks him to take her to the police, the driver starts ranting on about how his wife left him for another man. As he takes out a revolver, the Dark Angel appears in the back seat and Lana sees her waiting. The driver shoots himself in the head and the car crashes.
When Lana wakes up, she finds herself strapped to a bed at Briarcliff. Mary Eunice welcomes her back and tells Lana that the driver died in the accident and the paramedics brought the reporter to the sanitarium. Smiling, Mary Eunice tells Lana that she's back where she belongs.
At the motel, Jude finds Sam bleeding on the bathroom floor. As she tries to stop the bleeding, he tells her that one of her nuns attacked him. As she goes to the phone to call the police, she glances in the mirror and sees the Dark Angel kneeling over Sam's corpse. Jude sees the TV is on and someone has taped the newspaper article about Jude's hit-and-run to it. The person responsible has written the word "murderer" on the article.
Jude is at her hotel room when one of the band members she sings with, Terry, comes to her room. She claims that she was indisposed and missed their gig, and Terry assures her that another member's cousin covered for her. He then gives Jude an envelope with money and a business card in it and says that she's out of the band. Jude has been slipping for a long time and they realized that the cousin was a better singer by comparison. She accuses them of conspiring against her and then tries to seduce Terry into taking her back. Disgusted, Terry tells her that he's leaving and that the card is for a police detective who is talking to everyone at the club on the night of hit-and-run since the girl was hit near the club.
Once Terry leave, Jude packs her belongings and leaves. As she drives away, she hears a newscast about the police search for the driver. As she reaches for a bottle of whiskey on the seat, Jude loses control of the car and it goes off the road. When Jude wakes up, it's the next morning and she realizes that she rammed her car into a statue outside of a nunnery. When the nuns ask if she's okay, Jude looks up at the statue, wreathed in sunlight, and says that everything is fine.
Mary Eunice calls Sam's apartment, well aware that Jude is there. She tells the older nun that the evidence she planted will show that Sam was investigating Jude for the hit-and-run incident. Mary Eunice tells Jude to start running and then look at the nightstand to see what she left her. After the possessed nun hangs up, Jude checks the nightstand and finds a straight razor.
Jude leaves Sam's apartment and goes to a diner. She washes the blood off of her hands and then imagines slitting her wrists with the straight razor. However, Jude goes to a booth and finds the Dark Angel waiting for her. The nun tells the angel that suicide was just a passing thought, but the Dark Angel tells her that her song was more plaintive, but that she never judges. Jude wonders what was different and asks if it was different than the night that she told her husband that he gave her syphilis and he cast her out. The Dark Angel says that at the time Jude was young and still had hope. Jude wonders if her song was different on the night she hit the girl in the road, but the angel says that was the night that God showed her the way. The Dark Angel tells Jude that the nun deserves peace after everything she's done to try and find meaning, and that the end is very close. Jude agrees but says that there's something that she has to do first. Meanwhile, two waitresses watch and assume that Jude is insane.
The next day, Jude goes to the Stones, the parents of the girl she hit. She claims that she's Missy's Sunday School from fifteen years ago and that she has something to tell them. However, the girl, Missy, comes in from her night shift at the hospital. Jude is shocked to see her and explains that she thought Missy had died in the hit-and-run. When the Stones wonder why she came there, Jude tells them that Missy's accident inspired her to take her vows, but she has recently been questioning her faith. Mrs. Stone admits that her husband Hank wanted to kill the person responsible, but that she figured that the driver would suffer more by having to live with what they did.
When Lana wakes up next, she calls for Jude, but Mary Eunice tells her that now she's in charge. The reporter tells Mary Eunice about Thredson and Mary Eunice says that she believes her. She promises Lana that no one knows where she is and that she's safe. Mary Eunice then insists that Lana take some sedatives, but the reporter insists that she tell the police and have them search Thredson's basement. As Lana takes her medicine, Mary Eunice tells her that Kit escaped from police custody and that the authorities have issued a shoot-on-sight order.
Kit returns to Briarcliff to Grace and enters through the old tunnel as Arden's mutants follow him.
Grace is in the kitchen, recovering from her infection, when a nun finds her there. Grace doesn't want to go back to her room and the nun says that she can stay until she's done cleaning. Once she leaves the kitchen, Kit emerges from the shadows and tell Grace that she has to escape with him. As he leads her to the door, the nun comes back and sees them. Before she can sound an alarm, one of the mutant creatures comes up from the tunnel and savagely kills her. Kit attacks the creature and manages to disembowel it with a kitchen utensil, just as Frank comes in and sees Kit covered with blood. He fires at Kit and Grace jumps in front of the bullet, taking it for her lover. As she falls to the ground, the Dark Angel appears beside her and Grace says that she's ready. The angel kisses her and Grace's last words are that she's free.