Britten stumbles onto a dead body during a jog through the park. The M.O. matches the serial killer Gemini who was killed 12 years earlier, yet there have been more bodies in other cites through the years accredited to another killer. Britten wonders if this is all the work of an elaborate copycat or if Gemini is actually still alive. Gemini always killed in pairs, with a second victim murdered within 48 hours of the first and stashed in a similar location. Bird and Britten realize they have little time to find the perpetrator before he or she moves on to another town. The FBI is sending their Gemini expert from Portland to help with the case.
The FBI expert Elizabeth Santoro shot the original Gemini killer. She has spent the last several years following this copycat killer, and she's been writing a book about it. Santoro explains the real Gemini put a $2 bill in each victim's hand, something never released to the public, so when this detail is missing from a murder scene, the FBI knows they're dealing with a copycat. Britten concedes there was no $2 bill found on his victim. Not content to let it rest, Britten stalks and captures the stray dog that led him to the body in the first place. Examination of the dog's stomach yields a $2 bill. The dog must've taken it from the victim's hand.
Santoro isn't impressed by the $2 bill's appearance. She maintains it was probably a plant by someone with insider information, like a former law enforcement agent, trying to make the killings appear more exact. Bird challenges Santoro's assessment. He thinks this murderer could be the original killer, and they're wasting time following a profile instead of clues. To Bird's disappointment, the captain sides with Santoro. Later, Britten explains Bird's request - can't they just consider the possibility that Gemini is still alive? Britten admits mistakes are part of the job. and he's made his fair share too. While she doesn't doubt Britten has made mistakes, Santoro coldly sticks to her story. What none of the cops know is that there's a methodical, glove-wearing man out there somewhere, loading a stack of $2 bills into his scalpel case.
While Hannah is away in Oregon looking at potential law schools, Britten is looking for his phone charger. After he leaves her a message, Britten finds an estimate from the Mountain Top Movers & Storage Company for a move from Los Angeles to Portland in her nightstand. Britten tells Dr. Lee he's frustrated. These movers know she's more serious about this move than he does! Lee asks why Britten doesn't feel Hannah's serious about moving - is he only hearing what he wants to hear? Britten thinks that moving is a cop-out; it's easier than staying in Los Angeles and dealing with things. Reminding him that most marriages don't survive the loss of a child, Lee wonders if Britten's real fear isn't about Hannah leaving LA - but about Hannah leaving him.
Vega and Britten are following up a lead on a home invasion case when they find a closed-down store, covered in graffiti. Vega is upset because he paid $100 to get this address, and it was supposed to be a pawnshop. Britten lectures Vega: if you have to buy information, it might be true, but if someone's selling, it's always fake. When Vega wonders if the department will pay him back, Britten calls the lost money a Rookie Tax. Later, Britten sits in bed, holding the moving estimate. Why isn't Hannah picking up her phone or returning messages. Could Dr. Lee be right?
Ignoring Santoro's request to research disgruntled law enforcement personnel, Britten and Bird pound the pavement around the location of the first body. Gemini always used to kill his second victim within two miles of the first. After the partners split up to canvas motels, Britten notices the Mountain Top Movers & Storage sign on an abandoned building. Sensing the connection to his other world, Britten breaks into the building and finds a suspicious person inside. The suspect runs off as soon as Britten identifies himself, and he eludes Britten's pursuit.
Evidence found in the abandoned Mountain Top building includes a stash of $2 bills, which seems to connect the suspect to the killings, but nothing they've found is going to be conclusive DNA-wise. Santoro asks what led Britten to enter the building in the first place, yet Britten can only offer some flimsy excuse, as he knows any admission to using memories from his other life will sound crazy. Britten notices a symbol printed on a napkin, which matches the graffiti at the shuttered pawn shop he found with Vega. Was Vega's bad lead a clue for this case? Santoro is growing suspicious of Britten's unusual investigative methods and tells Captain Harper that he may well be the person planting evidence and committing these murders. He fits her profile as a disgruntled police officer. Still lurking in the building, the suspect overhears Santoro's conversation with Harper.
Gemini leaves a voice message at the police department, mocking Santoro. Britten got closer to catching him in one day on the case than she has in 12 years. Once the police trace the call back to Britten's home phone line, Santoro outlines how Britten alone found the victim and the $2 bill - and has offered no credible reason for entering an abandoned building, which just happened to contain clues. Britten can't believe she's still sticking to her story that Gemini is dead, especially after all the evidence they've found. More importantly, Rex is coming home in a few hours - and Gemini was making calls from his house!? When the dialogue gets too hot, Harper asks for cooler heads to prevail, but obviously, Santoro thinks she has her man. Harper asks Britten to surrender his weapon while they research the facts. Britten fears this is all part of Gemini's plan; now the cops are watching Britten instead of the real suspect.
The police search Britten's house for evidence as Bird talks to Britten in the interrogation room. Bird confesses he can't handle Britten since he came back to work after the accident. Everything is a hunch Britten can't explain, and they no longer feel like the team they once were. Feeling paralyzed, Britten still can't explain his predicament to his own partner. Despite all this, Bird doesn't think Britten's the killer and hopes Britten can pull another rabbit out of a hat by going over crime photos he purloined from the evidence room. Noticing the napkin with the graffiti mark, Britten asks for an image search. The graffiti mark is the same as a logo for a local coffee shop... A coffee shop that's got a location in the lobby of Santoro's hotel! Could Santoro be the killer's next victim?
Gemini abducts Santoro on the sidewalk outside Britten's house. When Santoro doesn't pick up Bird's calls, he puts out an APB on her and locks down all of the public parks in the surrounding area. Gemini is able to flash Santoro's FBI badge to the policemen standing guard to gain access to his desired park location. Once Britten and Bird find out someone got through the checkpoint, they hustle to the same area. After sedating Santoro, Gemini asks if she really thought she'd gotten the right guy all those years ago - or if she just wanted it to end. The killer hates that she told the world he'd lost. Gemini starts the first incision into Santoro's arm to begin the bleeding out process when he hears the detectives approaching. Gemini fires shots to create a distraction and flees. Britten focuses on Santoro, creating a tourniquet for her arm, and gets her to paramedics.
In the other world, Britten confronts Hannah about the moving estimate - does she want to move to Portland without him? Hannah admits she had Mountain Top come to the house, but she was too embarrassed to tell Britten that she wants to move, and that it gives her the kind of hope she hasn't had in a long time. Leaving town feels like an easy way to move past their grief, and yet she feels guilty for wanting it. Hannah doesn't want to run away, and she doesn't want to forget Rex. Every time she looks at Britten, she sees Rex, and that's something she would never want to leave behind.
Having renewed confidence in Hannah's commitment to their marriage, Britten tells both his therapists he'd have no problem moving to Oregon if she ultimately decides to do so. Neither of them understands how Britten could move there in one of his worlds and stay here in Los Angeles with Rex in the other. Dr. Lee believes the reason Britten's worlds work is due to the same visual landscape in both - and moving would break the fabric of both. Evans believes leaving would help the division between the worlds to erode and one would show itself to be what it really is... a fantasy. Britten remains defiant in the face of his therapists' theories. His two realities coexist because he makes them work, and he won't let anything change this.
Britten's stuck in traffic when Gemini calls. Gemini is amazed Britten's come so close to catching him in 48 hours, so he broke into Dr. Evans office to find out more about him. Gemini now knows Britten can't tell whether he's awake or asleep and bets Evans told him he's crazy. Gemini begs Britten not to let the therapists change him. "The world needs a few of us to see it... sideways." Camera pulls back to reveal that Gemini is at the airport, about to board a flight to Portland, Oregon. He hangs up the phone, leaving Britten with a lot to think about...