At the warehouse, everyone is in the office except Artie, who comes in late for their meeting. He explains that he got a message from Hugo Miller that he found an artifact. Artie sends Pete and Claudia to recover it and ignores Claudia's objections. Meanwhile, Myka and Steve are going to New Orleans to meet with therapist Nina Golden, who has reported that all of her patients have been cured overnight for the last three months. When Steve points out that they're going to recover an artifact that is doing good, Artie angrily snaps that they never know what artifacts can do. As the others leave, Artie tells Pete to keep an eye on Claudia, claiming that she's been under a lot of stress.
In New Canaan, CT, Pete and Claudia meet with Hugo, who explains that he's been wandering the world for a few years before coming back home. He shows them a bag of marbles owned by a young Bobby Fischer, and each one gives the user a strong focus but leads to violence, insanity, and possibly a stroke. Someone sent them to him by Fedex. Hugo's nephew Brady comes in and Hugo explains that he's staying with his uncle while attending the Tilson Academy, Hugo's old alma mater. Brady accidentally took the marbles to school and explains that there is a lot of pressure because of the Interschool Multidiscipline Tournament. Hugo thinks that nothing bad happened but Brady reveals that there are black throbbing veins on his arms and they're getting worse.
In New Orleans, Steve and Myka interview one of Golden's patients, Alex, who suffered from PTSD after the war. Yesterday his symptoms disappeared and Alex doesn't even remember having the condition. Golden confirms that all of her recent patients have reacted the same way. Steve is clearly unhappy that they're going to take away an artifact that helps someone. Myka asks if Golden has seen any new items in her office and the therapist says that she hasn't. Meanwhile, Steve seems fascinated by a painting of Death on Golden's wall.
At the B&B, Artie is heading out when Brother Adrian arrives at the door. He tells Artie that he has something that will show them who stole the astrolabe.
Pete neutralizes the bag of marbles but nothing happens. Claudia checks Brady's laptop and confirms that he loaned a marble to his friend, Tommy, who is currently beating up one of his fellow students. Brady admits that he loaned out three more marbles as well. They go to the academy and meet with Tommy. Tommy has the same black veins and is worried that they'll call his parents. He explains that he beat up the other kid because there was only one spot on the math team and the other kid was competing for it. The headmaster, Marshall, comes in and points out that they're all under pressure to generate more alumni support.
Myka goes through the files while Steve stares at the painting again. He insists that he's fine and refuses to discuss his feelings with Myka. She spots a poster for a jazz club, The Altered Scale, and they recognize the logo from the t-shirt that Alex was wearing. They go to the jazz club to see if any other patients went there.
Brady gives the agents the list of his other three friends. While Pete figures out what classes they're in, Claudia checks on Hugo, who is worried that he screwed up. She assures him that accidents happen. They split up to check out the three students and recover the marbles.
Brother Adrian shows Artie an artifact spur that belonged to Jack Hunter, a famous bounty hunter. They can use it to track the stolen artifact, but Artie says that Warehouse agents can't use artifacts per the Regent rules. Brother Adrian suggests that they do it anyway despite the risks but Artie continues to avoid trying to use it by saying they need to do a lot of research. The Templar has already done all of the research and Artie reluctantly goes to work.
Myka and Steve discover that the jazz club is filled with old relics. Steve still doesn't believe that there's a problem with a good artifact but Myka warns that artifacts always have a downside. They talk to the bartender, Dina Smith, who says that they haven't got any recent items. A band is playing on stage and Steve notices that one musician, Ethan Ellis, is the only one who plays every night. Ethan is playing a trumpet in style but they notice that he appears weak. Dina says that he's had a bug going on three months and the agents realize that he's in pain and it's connected to the patients who lost their pain.
At the academy, Pete finds one of the students, Declan, attacks his teacher when he refuses to put him on the bio team. Declan grabs a scalpel, swings at Pete, and then runs off. The agent chases and tackles him and recovers the marble. He then contacts Claudia, who is looking for the second student, Reggie. Meanwhile, Hugo and Brady track Pierce, the third boy, to a seminar. Hugo wants to wait for Pete but Brady focuses on getting the marble and his eyes turn black... and then he collapses.
Hugo takes Brady to the school nurse while Claudia searches the theater where a debate is beginning. Brady is getting worse and they figure that once they get the two remaining marbles, they're done. Claudia spots Reggie, who already has black veins spreading across his body. His father tells him to make sure that he's the last one standing, and Reggie goes up on stage and starts to drop a catwalk on his competitor. However, Claudia arrives and stops him just in time.
Artie has Brother Adrian close his eyes and picture the astrolabe, and then waves a matchbox artifact over the spur. Once Adrian opens his eyes, the spur melts and Artie claims that using one artifact to find another gets complicated. However, the Templar says that it wasn't the real spur. He says that he bought it to test Artie's intentions and accuses him of being foolish and selfish. Artie insists that he did what he had to and walks out.
Myka and Steve tell Ethan that someone is trying to hurt him and asks who might be jealous of him. He doesn't know of anyone and doesn't remember anyone giving him any items. He plans to play through the pain while he can and goes back onstage.
Claudia hauls Reggie to the nurse's office and he goes to check on Brady. Pete brings in Pierce, who explains that Marshall, the headmaster, confiscated his marble when he lost his temper in class. They try to work out what Marshall's goal is.
Marshall goes to a chemical closet and starts collecting cans of volatile substances.
Myka goes over the club records and discovers that Ethan didn't start playing until three months ago when he started getting good. Dina says that an old jazzman came in about that time, and the man said that to be a great jazz player, Ethan needed to experience more pain. She compares notes with Steve and they figure that Ethan is doing it to himself to play through the pain and become a real jazz player.
Marshall's secretary tells Pete and Claudia that the headmaster went to the gym where the final basketball event of the IMT is held. She admits that Marshall was mad at the board because of budget cuts and the agents realize that he plans to blow up the board and the students. Pete goes to the gym while Claudia collects Hugo, but Pete doesn't see Marshall there. However, Claudia and Hugo discover that Brady and the other possessed students have recovered to the point where they're ready to stop them from preventing the IMT any way that they can.
Artie goes to the Univille Diner but Brother Adrian follows him there and warns him that he can't walk away from it. He insists that Artie has to undo what he has done but Artie warns that there's more at stake than he knows.
Myka and Steve tell Ethan that he has to stop and explain that they know what he's been doing. However, Ethan refuses to hand over the artifact.
When Brady and the others refuse to back down, Claudia uses her Tesla to stun them and Hugo reacts in horror.
Artie tells Brother Adrian what happened in the original timeline and that the Templar was there. When Artie insists that he can handle the evil unleashed, Adrian asks if he can let the rest of the world live with that evil.
Ethan insists that he has what he wants but then collapses. When Steve says that it's killing him, Ethan insists that it's worth it. He grabs Steve's hand and tries to take away his pain, but reacts in shock.
At the academy, Claudia clutches at her chest in pain while Hugo admits that he showed Brady how to use the marbles. She realizes that Hugo wanted Brady to become a warehouse agent and he explains that he was greedy and wanted to leave a legacy. Claudia loses her breath while Hugo wonders if everyone is suffering for his mistakes.
Steve begs Ethan to stop and admits that he could be killing Claudia. Myka hears him and breaks the connection, and discovers that Ethan is using a cigarette case artifact. When she neutralizes it, Steve recovers.
At the academy, Claudia recovers and dismisses it as stress. She assures Hugo that both her and Brady will be okay. When he continues to blame himself, Claudia tells Hugo that he has to save his nephew by finding the last marble.
Artie refuses to undo what he has done, and Brother Adrian warns that he works with powerful people. He promises to dismantle Artie's life and warns that unlike the Regents, the Brotherhood follows no rules.
Pete calls Claudia and tells them that the entire school is in the gym and he can't find the headmaster. The school board comes in and Pete realizes that Marshall could strike at any moment. As the game begins, Hugo and Claudia arrive and Pete tries to work out where Marshall would hide. Hugo realizes that the furnace room is directly underneath the gym. Pete goes to investigate and Marshall knocks him out from behind. He takes Pete's Tesla and holds him at bay while he mixes chemicals to create a lethal gas. As he starts to pour the gas into the furnace, Pete grabs a pipe and knocks him out, and then calls Hugo. Hugo tells him to turn off the furnace but the switchboard is too complicated and Claudia can't get there in time. With time running out, Pete realizes that he needs to focus and takes the marble from Marshall.
Hugo and Claudia try to get everyone out of the gym without panicking anyone, but realize they can't do it in time. Pete focusses and remembers his eighth-grade classes, and then shuts down the furnace. He takes Marshall upstairs and neutralizes the marble just in time. With all the marbles neutralized, Marshall reverts to normal and the agents claim that contaminated mushrooms gave him hallucinations. Hugo thanks Claudia for what she said earlier about Brady. Brady comes in as Claudia tells Hugo not to be reckless with his nephew, and Hugo goes to Brady.
Ethan explains that Janis Joplin left his grandfather the cigarette case, and he used it to inspire himself. He insists that he was helping the patients as well, but Steve says that people have the right to work out their own pain. When Ethan says that it's a good time for him to die, at the top of his career, Dina comes over and says that he's being selfish toward the people that love him. Ethan realizes that she likes him while Steve and Myka go to get a drink. Steve explains about the connection between him and Claudia, but refuses to let her pay for his life with hers. He admits that he hasn't told Claudia yet because he figures that she'll stop him. Myka tells him that she has lost too many people and doesn't want to go through seeing him die again, and insists that there must be another solution. She suggests that Steve start looking for another solution.
Back at the warehouse, Myka explains that all of the patients recovered their original symptoms once they neutralized the cigarette case. Steve asks for time at the warehouse studying the metronome and Artie tells him to take all the time he needs. Claudia and Pete arrive with the marbles and she asks Steve why he looks so serious. As they go to watch Tivo, Artie asks Pete how Claudia was and Pete says that she was strong and determined. When Pete says that they recovered the marbles, Artie opens them and realizes that the Brotherhood sent them to Hugo to dismantle his life's work. He doesn't tell Pete about his suspicions but then goes to the aisles and discovers that the Brotherhood has taken the marbles and left a black diamond as their calling card.