Artie has a flashback to himself, lying in a darkened room. Mrs. Frederick appears and tells him that he's been there before and he'll soon remember it. He wonders if it's a dream and Mrs. Frederick tells him to go back to the beginning.
Artie snaps out of it and finds himself in his office. Pete and Myka check in from a zoo where their most recent artifact search has taken them. Artie admits he hasn't been able to find the source of the security breach into the warehouse yet. They tell him to get some sleep. Once they sign off, Artie has another flashback and Mrs. Frederick tells him to get up. A young girl runs by and Artie wakes up to discover that a young woman has handcuffed him. He doesn't know who she is but the woman says that she was a lot younger the last time they met. When she says she knew him when he was a professor. Artie realizes that she's Claudia Donovan and addresses her by name. He tries to leave and she electrifies the cuffs, stunning him. Artie says it was a long time ago and insists he wasn't responsible for Joshua's death. Claudia insists that he's responsible and now she's going to get payback for her and her brother.
Later, Pete and Myka return to the warehouse and discover the front door is open. They go inside and quickly realize that Artie has been abducted. As they try to find clues, Artie's Farnsworth rings and Mrs. Frederic wants to know what's going on. She insists that agents can't be taken out of the warehouse but is soon forced to admit it's possible. Mrs. Frederic tells them to use the durational spectrometer to identify everyone in the room in the last five hours, and that they're under lockdown and should stay there no matter what.
Claudia takes Artie to Joshua's old lab and he wonders what Claudia has in mind for him. She insists that Joshua isn't dead.
Pete uses the spectrometer and scans back for people in the room. They get an image of Claudia and thanks to his knowledge of lip reading gained from communicating with his deaf sister, Pete can tell that Artie called the intruder "Claudia Donovan." They start doing a database search.
Claudia is feeling ill but says she brought Artie there because that's where Joshua's presence is closest. She points out that Joshua screwed up, and Artie knows why he rushed his experiment.
Pete and Myka talk to Claudia's landlady, Mrs. Richman. The landlady reveals that Claudia checked herself into a psychiatric hospital six months ago, but checked herself out two months ago and hasn't been back since. They check out Claudia's room and discover that she has been trying to track Artie across the U.S. They also find a photo of a much younger Claudia with her brother Joshua.
Claudia tells Artie that Joshua has been visiting her. She mentions that Rheticus was right and Joshua was correct as well. Artie insists that Rheticus was nuts and the experiment could never work. Claudia insists the minerals in the metal should have worked but Artie doesn't believe it. She admits sheÃ¢ï¿½ï¿½s taken it as far as she can but now she needs Artie to keep his promise and bring Joshua home. Artie has another flashback and finds himself face-to-face with Joshua and his younger sister Claudia from 12 years ago. He snaps out of it and Claudia tells him she's been having the same vision. The lab starts to fill with electricity and Claudia starts choking. She tells him to sit down as a glowing ball of light flies through the lab. It resolves into an image of Joshua, reaching out to them for help. Energy flows from him to Claudia and back again before the Joshua image disappears. Claudia insists it was Joshua and since Artie saw it, she's not crazy. She wants Artie to help him bring Joshua back and explains she has everything there. Claudia wonders why Artie never tried to recreate the experiment and save Joshua.
At Claudia's apartment, Myka discovers that Claudia has a collection of books about Rheticus, a 16th century mapmaker and mathematician. She realizes that Claudia took one book with her.
Artie tries to warn Claudia how dangerous the experiment is but she insists she had to save Joshua. She hacked into Artie's files and discovered that he hadn't done anything to help Joshua in 12 years. Claudia figures he'll help because he feels guilt but Artie insists he doesn't. Claudia doesn't believe it but has a nosebleed. Artie figures it's been getting worse and her connection to the experiment is making her worse. Artie notes that Rheticus' experiment in human teleportation was dangerous and Joshua's more so.
Myka reads through the books on Rheticus and notices a post-it note next to a sketch of a 16th century metal compass. According to the books, no one ever saw it despite Rheticus' claims that he owned it. Pete figures that it's an artifact.
Artie reviews Claudia's equipment and notes that the compass disappeared with Joshua. She admits that she doesn't have anything to replace it and admits she needs Artie's help. He threatens to shut her down but for her own safety but Claudia accuses him of abandoning Joshua again. She talks of how Joshua gave up his life to raise her and she owes him, and so does Artie.
Artie calls Pete on his cell phone and tells him that he's okay and he's taking time off to help a friend. He tells the agents to stop looking for him but Myka warns him that Claudia has been under observation at a psychiatric hospital. Artie still insists on helping Claudia and hangs up rather than hear Myka's arguments. The agents head back to the Warehouse while Artie brings his emergency travel kit's equipment from his car to the laboratory.
Pete and Myka return to the warehouse and find Mrs. Frederic waiting for them. Myka points out it would be nice if they could contact her, and explain that they had a lead. They realize that Mrs. Frederic knows where Artie may be. She tells them to go through the Rheticus artifacts and they have to learn how Joshua messed up Rheticus' teleport experiment. Mrs. Frederic refuses to tell them where Artie is, warning that if they go in empty-handed then they'll be lost just like Joshua was. She tells them to understand Rheticus, which will give them the key to the compass and the experiment's failure.
Artie uses the Ben Franklin lightning rod in his emergency travel kit to substitute for the compass. He admits he knows she was in a psych ward and offers his condolences. Claudia finds Joshua's journal and they go through it.
Myka and Pete go through the Rheticus gadgets but don't find anything significant. Checking Artie's notes, they realize that Rheticus had an insistence on rules and order. Pete realizes that the gadgets have secret panels that contain inscriptions with further instructions.
Artie prepares to boost the power through the lightning rod and Claudia warns that Joshua is coming. Artie has another flashback and finds himself in the laboratory 12 years ago. Joshua is there with young Claudia. In the past, Artie insists that the rumors about Rheticus and his experiment are just that but Joshua doesn't believe it. He shows past-Artie Rheticus' compass and insists he can duplicate the teleport experiment.
Artie snaps back to the present and prepares to lock on to Joshua and hold him in pace prior to bringing him out. Claudia collapses and Artie goes to her. The Joshua image appears again.
Pete and Myka find the various inscriptions and realize the compass had inscriptions. However, he didn't find the hidden inscriptions, causing the experiment to fail.
The phantom Joshua starts draining energy from Claudia and warns Artie that there's not enough power. Joshua warns that Claudia and Artie are tied to him now and the lab is becoming increasingly unstable. The next time he arrives, it will kill Claudia. Joshua tells Artie to overload the equipment using the lightning rod, and he'll die but save Claudia. He disappears again.
Myka and Pete report to Mrs. Frederic and explain that Claudia must have taken Artie to the lab. Mrs. Frederic is pleased at their initiative in Artie's absence and Myka wonders if Artie is going somewhere. She tells the agents to get to the laboratory as quickly as possible.
Claudia wakes up and thanks Artie for his help. He has another flashback-vision of himself telling Joshua that the people who want the teleportation device are coming for it now and Joshua has to protect himself and his family. Past-Artie promises to protect the compass and past-Joshua goes to get it. He asks past-Artie to watch over young Claudia.
Artie snaps out of the vision and prepares to destroy the teleportation equipment. She tries to get him to stop and then winces in pain as Joshua starts appearing.
Past-Artie worries that past-Joshua hasn't come back yet. He takes young Claudia's hand and goes to the lab, promising he won't let anything happen to Joshua.
Claudia collapses and present-Artie promises to save her. Pete and Myka break in.
Past-Artie arrives in the lab to see past-Joshua using the compass to power the teleport device.
Present-Artie is angry the agents followed him. They explain that Joshua didn't have all the rules and the vital inscriptions are inside the compass. As his nose starts bleeding, Artie remembers that the compass disappeared with past-Joshua as young Claudia looked on.
Present-Artie grabs Claudia and steps into the teleport field, realizing what he has to do.
Past-Joshua promises young Claudia that he'll always love her.
Present-Artie and Claudia look on as Joshua appears. Artie reaches out to him and the three of them disappear in a burst of energy.
Artie and Claudia are reunited in another dimension with Joshua, who hasn't aged in 12 years. Artie finds the compass but can't decode the inscription showing how to open the hidden panel. Claudia suggests he use "Thomas," after a poem about his lost love, someone named Thomas. The name opens the panel and the instructions explain how to turn the dial. They touch the compass together and turn the dial, and are returned to real space. Artie assures his friends that he's okay while Claudia and Joshua embrace.
Back at the bed & breakfast, Artie congratulates the agents on their work. As they leave, Myka offers him a sympathetic ear if he wants to talk about losing someone on the job. He says he doesn't but then offers to talk if she ever wants to talk about losing someone on the job.
Later, Mrs. Frederic comes to see Artie. He admits he had to go back and take care of his responsibilities to Joshua. He pushed Joshua to try it and as a result he was lost for 12 years. Mrs. Frederic notes she might have been able to save "Gus," but didn't. She tells him they can't save everyone, but that's not why she's there. Mrs. Frederic warns Artie that Claudia knows too much. Artie insists that she wouldn't hurt them. Mrs. Frederic warns that others might and Artie knows what options they have to deal with her.