As his worry about Claudia grows, Artie sends his protege into the field with Pete, while Jinks and Myka head to Louisiana to investigate several psychiatric patients who have made miraculous turnarounds. The common thread is a musician, who Myka and Jinks discover is taking others' pain in order to improve his playing, though they don't know how.
Claudia and Pete reunite with former agent Hugo, who finally found his marbles...well, Bobby Fischer's marbles...well, most of Bobby Fischer's marbles. Hugo let slip to his nephew, Brady, who's attending a highly competitive prep school, that the marbles increase focus, and Brady, after using one to write a paper for the school's intramural competition, loaned four of them to his classmates. The downside of these incredible marbles is that they make the user incredibly violent.
Claudia and Pete manage to track down three of them, but the fourth was confiscated by the headmaster, and no one can find him. Anyone who uses the marbles experiences a strange throbbing in their veins, and if unabated, the rage in their veins could destroy them. Claudia and Hugo try to meet up with Pete to find the headmaster, but on the way, Claudia gets the wind knocked out of her. Miles away, Myka and Jinks have finally confronted the musician, Ethan, about his skill, and greedily, he reaches for Jinks to try to remove his pain. But Jinks's travails are more than Ethan bargained for, and as he siphons off the pain, Jinks senses that Claudia is choking. Finally, Myka severs the connection and bags the artifact, and Jinks confesses that he intends to stop the metronome in order to save Claudia. Myka asks him to look for another way before doing anything rash, and Jinks agrees.
Pete finally locates the headmaster in the boiler room, who is busy creating a vapor that will kill the members of the school board as soon as the furnace gets hot enough. Pete knocks the headmaster out and attempts to shut down the furnace, but the mass of wires and fuses is too much for him. He grabs hold of one of the last remaining marble and a schematic appears before him - he understands the wiring and shuts down the furnace. Claudia bags the marble and everyone goes home.
But that's not the end of the story, for Father Adrian has informed Artie that he knows he was the one who used the astrolabe. Adrian begs Artie for his help, but Artie says he will never undo what he did that night. He's unable to tell Adrian about the loss of hope the world would've undergone without his actions, so Adrian makes Artie his enemy. He leaves, saying that his brotherhood has already taken steps to reverse Artie's work, and when Pete delivers the marbles to him, Artie realizes that the Knights Templar may have already infiltrated the deepest workings of the Warehouse.