Pete and Myka are in Denver pursuing a jewel thief who is using an unidentified artifact to rob jewelry stores. As they climb over a fence in pursuit, Pete gets a call from Kelly, who wants to talk about their upcoming weekend together.
At the warehouse, Artie and Leena are cataloging artifacts while Claudia discovers a report about Trueheart Insurance VPs in Hartford, Connecticut, who are donating 50% of their money to free clinics. Impressed, Artie tells Claudia that she'll be coming with him since Pete and Myka are handling the jewel theft case. Claudia isn't sure that Artie has what it takes any more, but he objects and she quickly drops the matter.
Pete manages to grab the thief and yank the bag away while Myka pursues the man into a warehouse. She loses sight of him and comes across a security guard that the thief knocked down in his escape. Myka goes out a nearby window to find the man. Pete follows, dropping roughly and spraining his leg. There's no sign of the thief and they examine the bag. Inside is the artifact, a griffin statue. They figure that now they can relax and enjoy their weekends: Pete is going to stay in with Kelly, and Myka is going to her high school reunion. She claims that the football captain, Kurt Smoller, invited her personally, but finally admits that she merely tutored him in math. As they put the griffin in the neutralization bag, both agents eyes' glow yellow. They don't realize it and head back for the warehouse.
Later, Pete finds Leena sorting artifacts in the warehouse's canned food aisle. She notices that he's limping and suggests that he stay in bed, and he admits that he plans to do that at the B&B... with Kelly.
Artie and Claudia go to Hartford and Artie talks to one of the VPs, Howard. Howard insists that he did nothing wrong but soon realizes that the man now hates his wife and is in love with another woman. Artie goes outside and meets with Claudia, who has determined that two other VPs have fallen under the same spell. She checks their accounts and discovers that all three of them went to the same place, Hansen's Bar. Artie goes over the receipts and realizes that they all three bought someone an apple mojito. They figure that the person is the one with the artifact, and her next target is the last unaffected VP, John Donley. They talk to the receptionist, Teri, and learn that Donley is going to Hansen's Bar.
That night, Pete and Kelly finish making love and he apologizes for his leg. She insists that he's fine and Pete assures her he has no intention of going anywhere.
Myka goes to her reunion in Colorado Springs and chats with the hostess, Megan. They both spot Kurt Smoller, looking better than ever.
Artie and Claudia go to Hansen's Bar and find Donley. He's buying an apple mojito for a woman, Lauren Andrews, but rebuffs her efforts to seduce him. Donley starts to walk away but then turns and returns to Lauren, insisting that she fascinates him.
Kurt comes over to see Myka, who is drinking alone at the bar. He realizes that she's his math tutor in high school, and admits that Megan is the one who sent her the invitation. Myka wonders if he's still involved with Megan, and Kurt admits that they broke up after high school. He invites Myka over to talk with the other guys from the football team, but Myka passes.
At the bar, Donley is now desperately in love with Lauren. Artie, watching, figures that Lauren is using some kind of seduction artifact. Claudia, operating on her own initiative, monitors Donley's bank account to see when he makes any withdrawals.
At the warehouse, Leena unbags the griffin statue and sets it down. Its eyes glow yellow and it rotates on its own.
As Pete goes to get some food, he suddenly staggers in pain. At the reunion, Myka does the same thing. After a few seconds they realize that they've switched bodies. Pete-in-Myka calls Myka-in-Pete, and they compare notes. They realize the griffin is responsible and they have to get it from the warehouse and get back together to undo the switch. Myka-in-Pete realizes that the ex-alcoholic Pete-in-Myka is feeling the buzz from the drinks she was putting down, and tells him to wait and she'll drive to get him. However, Kelly comes out and Myka-in-Pete hastily tries to make some kind of an excuse about being called away on IRS duty. She's surprised and a little upset since they had planned to be together the entire weekend. She tries to get Myka-in-Pete into the warehouse but Myka-in-Pete gives her a brotherly kiss and quickly leaves.
At the reunion, Kurt and the guys are discussing sports when a slightly drunk Pete-in-Myka comes over, sits herself down, and starts talking sports, much to Kurt's surprise.
Claudia spots when Donley transfers $3 million out of his account to a free clinic. Lauren sends him away and Artie treats himself with several artifact-nullification devices. He then approaches Lauren and identifies himself as a Federal agent, and demands to know how she's seducing men. She shows him her leg in an attempt to seduce him while Claudia takes more photos of the woman. Artie finally walks away and tells Claudia that the investigation is over. As they go outside, he irrationally insists that there's nothing else to do. Donley attacks Artie, insisting that Lauren is his. Artie viciously fights back, insisting that Lauren is his woman, and prepares to Tesla Donley impotent. Before he can do so, Claudia intervenes and stops him. Donley sees what appears to be Lauren driving away. He tries to block the car but she runs him over and drives away.
At the reunion, Pete-in-Myka impresses Kurt with his knowledge of the Three Stooges. The ex-football captain admits he didn't know Myka was so much fun and tries to kiss him/her. Shocked, Pete backs away just as Myka-in-Pete arrives with the griffin. Pete-in-Myka quickly leaves and they go to her hotel room. As the drunken Pete-in-Myka tries to open the door, Myka-in-Pete is happy to learn that Kurt likes her. However, Pete-in-Myka points out that he's the one that Kurt really likes.
Artie and Claudia go back to their hotel room and Artie starts writing sappy poetry. Claudia confirms that Lauren's brother died six months ago of a medical condition and the insurance company refused to cover his expenses. They both figure that it's revenge, but now Lauren won't stop at simply taking money: now she plans to hurt people. Claudia examines the photos she took of Lauren and realizes that each time she showed the man her leg. Artie prepares to go to Lauren's house to declare his undying love, but Claudia stalls by suggesting he take a shower first.
At Myka's hotel room, the agents examine the griffin and discover that it's actually a bookend, one of a paired set. They put it down and test what Leena said, and discover that it rotates on its own. They figure that it's orienting on the second griffin and prepare to go. However, Kelly calls to talk to Pete, and Myka-in-Pete takes the call. She goes to the next room to talk to Kelly in private and promise her something to make it up to her.
Once Artie finishes with his shower, Claudia suggest he go to the closet to get his hat. She then handcuffs him to the rod and leaves to get the artifact.
Pete and Myka head out of the hotel with the griffin. As they set it down to triangulate, it turns toward the elevator and the security guard from earlier, Albert, comes out, holding the other griffin. They figure he's working with the thief, but he tells them it's much more than that. He "flashes" and turns into the thief, Victor. They attack Pete and try to get the griffin, slamming him back against Myka. Pete and Myka merge, and Pete is there by himself. He fights back but then morphs into Myka, and then back again. Victor and Albert, trapped in one body, keep switching as well. Myka finally manages to knock out his opponent.
Claudia goes to Lauren's house to get the artifact. Lauren greets her and tells her to leave, and says that she wasn't the one who hit Donley. Howard comes out, holding a gun, and captures Claudia.
Pete hauls the merged thief/guard back to Myka's room, but Kurt comes by. Pete morphs into Myka, who tries to tell Kurt that she doesn't want him there right now. She starts to close the door and Kurt pushes it back open, and finds himself facing Pete. Pete tells him that he took his best shot but now it's time to go, and shuts the door in his face.
Howard handcuffs Claudia to the stove and Lauren to a pillar, and then prepares to leave with Lauren. As he goes to get their bags, Claudia admits that she handcuffed Artie and there's no one that will come to rescue them. Lauren admits that she wanted revenge but now things have gotten out of control, and that she's using a pair of stockings to influence men.
Artie gets the iron out of the closet and turns it into a crude electromagnet, and then pulls his bag over to get the handcuff keys.
Pete tosses the thief/guard in the shower and sprays water on them to wake them up. He asks how they can undo the process, and the merged pair starts to answer. However, they start morphing faster and faster and explode as both of their bodies materialize at the same time in the same spot.
Howard comes back and prepares to shoot Claudia. However, Artie burst in and shines a light through a lens from the Lighthouse of Pharos, blinding the VP. Artie frees Lauren but prepares to leave with her. Artie tosses away the key to Claudia's handcuffs and heads for the door.
Pete and Myka call Leena, who does some research and determines that Robert Louis Stevenson, the creator of Jekyll and Hyde, He owned the bookends, and a photo shows they are an eagle and a lion. The agents realize that the heads of the two bookends were switched, and reversing the swap will undo their own swap. They start to pull the heads off but the morphing process accelerates toward its fatal conclusion.
Howard tries to stop Artie from leaving, and insists that he'll die rather than lose Lauren. Artie prepares to kill him and Lauren runs to get the stockings. She gives them to Claudia and together they manage to shred them. A wave of purple energy is released, negating the seduction spell and restoring Artie and Howard to normal. Howard leaves to find his wife, while Artie thanks Claudia for looking out for him. Lauren explains that she found the stockings in a box of item that her great-grandfather brought back from World War I. Artie recognizes the name of the owner as Mata Hari, one of history's most famous seductresses. Artie then leaves Claudia handcuffed, telling her to figure out one of the nine ways that she can use to escape her predicament.
With time running out, the constantly morphing Pete and Myka manage to switch the heads of the bookends. They're split apart and restored to normal. The agents realize that even on their weekends off, there's no way they can have a normal life.
Pete and Myka call in and inform Artie of what happened, and how the thief and guard worked together to rob the jewelry stores and make the perfect escape by switching bodies. As they leave the hotel, Myka spots Kurt and goes over to talk to him. She insists that there's nothing obvious about her, and Kurt points out that she was a lot more fun when she was just one of the guys. Myka asks if he wants to stay in touch and Kurt agrees. He gives her a goodbye kiss and Myka can't resist asking which kiss was better. Kurt admits the most recent one was, and points out that "Myka" burped when he kissed her before.
Later, Pete brings Kelly up to his room, which he's decorated with balloons, flowers, and rose petals. Kelly is impressed, but is more impressed because what he said on the phone was so beautiful, and it's clear that "Pete" understands her so well. Pete tries to find out exactly what "he" said, but Kelly gets him to the bed and they move on to other things.