A woman sees another woman die in a hospital bed, writes on her hand, and runs into the street, where she stands disoriented. Emily - driving down the same street - hits her.
The woman asks her if "he told her to make it look like an accident," adding, "he killed Rose; now he's coming after me." Who? "Charlie" (the name on her hand). She refuses treatment, claiming she's only 24 years old. (She's clearly not.) Can Emily take her home? She gives her an address and her name: Veronica.
When they arrive, Veronica says that it's the wrong address and wonders who wrote "Charlie" on her hand. Emily texts Cal for help. Minutes later, Veronica's telling Cal that Rose was her sister. When he drapes a coat over her shoulders, she calls him "Burt" and kisses him.
They bring Veronica to the Lightman Group offices. Eli stumbles in, face bleeding. When Ria tends to his wounds, Veronica takes over. Gillian tells Cal that Veronica isn't schizophrenic or on drugs, but suffers from early Alzheimer's. Cal asks her to cross-check "Burt" and that address.
Meanwhile, Veronica recites medical facts, adding that she met Burt when she was a nurse and he changed her life. When Emily asks what went wrong, Veronica returns to tending Eli and repeats the same facts.
Gillian tells Cal that Burton and Veronica Sloan lived at that address. They moved ten years ago. Burt's been dead three years. Also, Rose was a 1968 unsolved murder victim - and the only suspect was Veronica.
Cal and Gillian visit Veronica's brother-in-law, Gus, who says that the elder care facility didn't tell him Veronica was missing and that Charlie's a figment of her imagination. Cal says that Veronica's ill, not paranoid.
Gillian, Eli, Ria, and Emily listen to a tape of Veronica's 1968 police interrogation. Ria hears survivor's guilt. Eli hears rehearsed dialogue, and Gillian hears that she's hiding something.
After returning Veronica to the facility, Cal persuades the chief of staff, Dr. Hammer, and resident psychiatrist, Dr. Olson, to keep her off medication for now.
As Cal, Emily, and Veronica watch vintage home movies celebrating her engagement, Veronica walks up to and caresses the screen. Charlie Eaton, she says.
Cal confronts Charlie at his home, noting that Rose - his finance's sister - died the day Charlie volunteered for Vietnam. Charlie orders him away.
After examining more vintage photos of Veronica, Rose, and Charlie, Cal notes that within a two-month span the trio is no longer as tight - and Rose is pregnant.
Cal revists Charlie, who confirms the pregnancy, claiming Veronica's anger caused his sudden exit - but he didn't kill Rose.
Gillian thinks Veronica is using Alzheimer's to mask her guilt. Cal orders Veronica brought to her old address, where he'll "resurrect Burt," as that's who Veronica thinks Cal is. When Veronica arrives, she becomes jealous of Gillian, names four people Charlie murdered, and claims that Rose didn't want to have Charlie's baby - which Cal contradicts. Veronica then admits hiring a woman to terminate the pregnancy, during which Rose died.
Cal says that Veronica is guilt-wracked with more contempt for herself than Charlie. Gillian notes two of the people she named were recent deaths. She's mixing up the past and present.
Cal exits Veronica's room, eyes 26-year- old Mark - who's been in a coma eight months - and is accosted by Frank, who says that Veronica always lifted his just-deceased teenaged daughter Gretchen's spirits, so she wanted her to have a hand-painted card that reads "from Rose." Frank explains that's what Veronica called Gretchen.
After Gillian reports 12 residents of the facility died in the last six months and Veronica identifies a photo of Gretchen as Rose, Cal believes the Charlie she's scared of is on staff and killing people.
Cal and Gillian interrogate Dr. Hammer, who denies that there's an "angel of death" on his staff. All the staffers display "professional numbness" - except Frazier, who dislikes his job, but claims to draw inspiration from the patients' fight, adding that he and Dr. Olson are the only ones who care.
Cal revists the facility, sees another dead patient being wheeled away, and - as he confronts Dr. Hammer - spots a door moving. Cal returns to Veronica's room and finds Dr. Olson. Cal accuses him of playing God and killing Gretchen. Doctors play God all the time, replies Olson, putting on his white coat as he leaves - which causes Veronica to call him "Charlie." (Flashback to home movies of Charlie putting on a white coat, which Cal explains triggered Veronica's reaction.) Veronica says that Charlie knows she killed Rose while trying to abort his baby, so he wants to kill her.
Cal goes home and finds Eli, who explains his injuries as "research." Cal says, "If we do what we do right, it's gonna hurt - but don't push it."
Back at the facility, Dr. Olson gives Mark a fatal injection. Cal arrives, tells Olson that shot was just a saline solution (Cal switched it earlier and Mark was Eli in disguise), and he had no right to do that. Olson says he just wanted to prevent pain.
Cal tells Veronica that Charlie's gone and he's leaving. She calls him Burt, turns, and starts playing the piano that Gus and Emily brought in.
At home, Emily discovers that Cal has locked her car's steering wheel. He asks her to choose between her phone and the car. She dials her boyfriend, Liam. Cal takes the keys.