Allison dreams about an old "Ripley's Believe It or Not" story about Phineas, a man who in 1848, survived an accident where an iron rod impaled his head. After his body made a full recovery, Phineas changed from a hard worker to a drinking, fighting, profane man. During a long bender, Phineas introduced himself to another bar patron as Cyrus Ames. Ames was a notorious gunfighter and card cheat who had worked as security for the railroad. He was in the same doctor's office, dying of syphilis in the bed next to Phineas. Did a soul transformation happen that day?
At the office, Allison follows an errant paper which leads her to a Phineas look-a-like sitting with a woman. Devalos asks her to come to his office for a meeting with him, Scanlon and the couple, whom he introduces as Joel Tiernan and his wife Gabrielle. Gabrielle is an old friend of Devalos. Devalos says that Gabrielle's sister Robin was murdered in her Seguato Lake cottage six months ago. There were no witnesses or suspects, and Gabrielle suspected that the D.A.'s office, then run by Van Dyke, had given up on the case. Now that Devalos is in charge, he wants Allison and Scanlon to investigate the case.
While looking at the crime scene pictures, Allison has a flash of Robin in her cottage threatening a man, "I'm going to tell her everything." He becomes enraged and begins to throttle Robin. After Gabrielle and Joel leave, Allison tells Devalos that she thinks she saw the killer's face and wants a sketch artist. Meanwhile, Joe picks up Brigitte and Marie from school. Brigitte says she got in trouble for drawing a naked picture of her art teacher. She hands the drawing to Joe and says he and mom have to sign it so the teacher knows they both saw it.
Allison shows Devalos the police sketch of the man she thinks killed Robin. He becomes disturbed when he sees it, and then pulls a book from a cabinet. He shows the author's picture on the sleeve to Allison and asks if that's the man she saw. She confirms it is. The man is Gabrielle's first husband Nathan, a successful author who died two years ago in a head-on collision with a stolen car. He had been on his way home from a writer's retreat, and his death left Gabrielle a very wealthy woman. Devalos says Nathan couldn't have killed Robin.
That night at home, Joe can't stop staring at the very anatomically accurate picture that Brigitte drew of her teacher. Allison says it's perfectly normal for girls to draw naked pictures of boys, which is hard for Joe to swallow. Allison dreams about Nathan's car crash. On a deserted road, paper falls like confetti over two smashed cars. The driver of the stolen car, who Devalos said was never found after the accident, gets out. He stumbles over and pulls a paper off Nathan's face and sees he's dead. When Allison gets a good look at the other driver, she sees that it's Joel, Gabrielle's current husband.
The next day, Allison tells Scanlon about her dream. Both think Gabrielle doesn't know that Joel was the other driver. Allison thinks that's how Joel got the scar on his forehead. Scanlon wants her to be sure it was Joel. During his questioning of Robin's friends, Scanlon learned that Robin had a year long affair with Nathan. When he wanted to end it, she threatened to tell and things got physical. The friend saw bruises on her neck, but Robin told her she had fallen. Allison realizes that's what she saw in the flash.
Joe tells Allison that Brigitte's art teacher, Mr. Enright, and a school counselor want to meet with them. At the meeting, they find Brigitte has drawn another naked picture of Enright. Enright and the school counselor want Brigitte to have some counseling sessions to see if she's been exposed to anything that could cause her behavior. Joe becomes defensive, but Allison says they'll speak to Brigitte first. Brigitte tells them she feels compelled to draw the pictures. Joe worries Enright is putting off "naked vibes" and wants Brigitte to switch teachers. Allison says that nothing inappropriate happened and is convinced it will pass.
Scanlon calls Allison. He learned the city destroyed both the cars in the accident, but that Joel has a record of car theft. Allison asks him to check on the papers she saw in her dream, but Scanlon says there weren't any. He tells her to concentrate on Robin's murder. That night, Allison dreams that Joel is telling Gabrielle he's really Nathan in Joel's body. He's reciting their history, a la "Ghost," of things only Nathan could know.
Allison visits Gabrielle at her house and tells her about her the soul-switching Phineas dream and how it relates to her case. Gabrielle tells her about the miracle of Nathan coming back to her through Joel. Neither had known Joel before the accident. Allison learns that Joel wasn't with Gabrielle the night of Robin's death, but she says it was hard for him as they were very close. Allison wonders if she knows just how close. At home, Joe finds Brigitte sobbing in front of a bunch of drawings that she drew of a naked Mr. Enright. She says she's sorry, but she just couldn't stop.
At work, Allison tells Devalos that Joel Tiernan is Nathan Cafferty. He thinks it sounds insane. He's surprised to learn that no one asked Joel where he was the night Robin died, so they bring him in. Devalos tells him about Allison and Gabrielle's conversation. Joel plays that down as his wife being very spiritual and romantic. When asked, he says he was sick the night of Robin's murder. Scanlon mentions the blood found at the scene, and Devalos asks him for a DNA sample to rule him out. Joel becomes angry and refuses to give one, saying it would cause Gabrielle needless stress.
At home, Joe tells Allison about Brigitte's meltdown. He shows her the drawings and wants Brigitte to stay home from school until it passes. Allison disagrees, then notices that all the drawings have a mark on the same spot on Enright's chest. Joe, surprised at the revelation, wonders if she's diagnosing him. Allison dreams of Joel watching the news of Nathan's death and learning about his fortune. The news downplays rumors that Nathan was working on a new manuscript at the time of his death. Behind Joel sits that very manuscript, Nathan's autobiography. He recites it, having memorized it. It's about the history of Nathan and Gabrielle's love.
Allison tells Devalos about her dream, and that Joel is a fraud who memorized Nathan's autobiography that he stole from the accident scene. She wonders why Joel killed Robin. Devalos thinks maybe he didn't. They show her Arthur Colbert's file, a maintenance man at the cottages who sexually assaulted a friend two months ago. His DNA matched the blood found in Robin's cottage. Colbert says he cut his hand doing maintenance in the cottage, but Scanlon doesn't buy it. Allison asks if they are going to do anything about the fraud. Devalos says he doesn't plan to, as they have no proof of it.
At Brigitte's school, Joe talks to Enright about the dot that Brigitte drew on his chest in her drawing. He suggests if he has a mole on his chest, he get it screened for skin cancer. Later, Allison dreams that Robin invites Joel to her cabin. She comes on to him, seeing how he'll react, since Gabrielle told her that Joel is really Nathan. Joel refuses her advances and she calls him on his bluff, saying he'd know about their little secret if he were really Nathan. She threatens to tell Gabrielle, and Joel kills her with a fireplace shovel.
Allison tells Gabrielle that Joel is a fraud. At first, Gabrielle is resistant but Allison convinces her. Later, Joel arrives home and isn't happy to see Allison in the house. Gabrielle says it's okay, that Allison knows about the soul swap and is here to offer some theories about him. Gabrielle asks why he hasn't written anything in two years, unlike the real Nathan who always wrote. They ask him to write something for them. He doesn't want to, but reluctantly agrees. He sits in front of the lap top, but can't do it. Allison asks him if he can even type.
After searching the house for the manuscript, they come up empty. Allison asks if Joel is just going to get away with it. Scanlon doesn't know what else they can do without the manuscript, but at least Gabrielle has kicked Joel to the curb. Allison sees that same piece of errant paper, which leads her to the lake by the house. It floats on the water, where a bobber pops up. She grabs the bobber, which is attached to fish line. At the end of it is the manuscript wrapped in plastic, perfectly preserved with Nathan's blood still on it.
At home, Joe tells Allison that Mr. Enright couldn't stop saying nice things about Brigitte, and that he's encouraging her to draw anything she wants whenever she wants. They figure that the dermatologist confirmed what Joe said about the mole in time to do something about it. They're pleased about Brigitte's latest drawing, which is of them, sans marks and with clothes on.