Previously in this series: In the wake of a house fire that killed his mother, 14-year-old Nick Slate, his younger brother, Danny, and their dad moved from Tampa, Florida, to Colorado Springs, Colorado. They planned to make a fresh start, living in the long-abandoned house of Great-Aunt Greta. When Nick chose the cluttered attic for his bedroom, he held a garage sale to dispose of numerous, ancient appliances stored there. Only later did he and new friends Mitch, Vince and Caitlin realize the “appliances” were really pieces of an elaborate machine created by the great scientist Nikola Tesla. It was known as the Far Range Energy Emitter (or FREE). When the partially reconstructed FREE lead to a nearly world-ending meteorite collision, Nick realizes he has to collect the rest of the pieces. Dr. Alan Jorgenson and his secret group of corrupt scientists, the Accelerati, try to get Nick to turn over the FREE. Nick refuses.
In Edison’s Alley, Jorgenson meets with the top-secret Accelerati boss and renews his commitment to get hold of Tesla’s technology. Meanwhile, Nick and Caitlin try to locate and buy back the pieces they’ve dubbed Teslanoid Objects. Nick asks out Caitlin on a date. She’s still confused about her feelings and still technically dating a boy named Theo, so she refuses.
Vince, who died in the previous book, is reanimated when Nick plugs him up to Tesla’s battery. The sight and smell of him are ghastly. If he ever comes unplugged, Nick or one of his friends has to reattach him quickly so no one realizes he’s undead.
Petula still dates Mitch, even though she thinks he’s an imbecile. In the previous book, Accelerati spy/lunch lady Ms. Planck recruited Petula to work for the Accelerati. But now Petula is tired of just taking pictures that shows what will happen 24 hours in the future. She feels she’s being used for the Accelerati’s financial benefit. When she conveys her dissatisfaction to Ms. Planck, the woman tells Petula she’ll introduce her to some of the higher ups in the secret society.
As Nick and friends continue to hunt for Teslanoid Objects, Nick discovers that a boy on Danny’s baseball team may have purchased some special stain remover at his garage sale. The boy’s mother, Beverly, and Nick’s dad seem to be developing an interest in one another. Nick does his best to undermine the budding relationship while finding out how to get the stain remover.
Nick and Mitch are tracking a Teslanoid harp. Petula and Ms. Planck beat them to it. When the owner, in her 30s, plays the harp for them, they realize she is playing on cosmic strings made up of invisible threads that stretch across dimensions. Petula is mesmerized, but Ms. Planck warns the girl not to touch the invisible strings. As they leave, Ms. Planck plants a device that makes the woman and her surroundings age quickly, until the woman is a skeleton. Petula plays one string on the harp and feels it has told her to “complete the circuit.”
Although the boys are unaware of Petula’s involvement, they realize the Accelerati beat them to the harp. Nick feels like the machine in his attic is crying out to be completed. Since the asteroid nearly hit Earth, the planet has been experiencing an increased amount of static and frequent electric shocks. Strange issues with Earth’s magnetic force have caused numerous problems with aircraft navigation. Nick wonders if Tesla’s machine may somehow remedy the problem. He asks Caitlin to meet him and tells her he thinks Tesla had figured out a way to harness energy generated by the asteroid. He believes it’s up to them to finish the inventor’s life work.
Caitlin, who now feels ready to date Nick, can see his thoughts are elsewhere. She tells him she’s concerned about his obsession with Tesla and the machine.
The next evening, Jorgenson and some of his team go to Nick’s house to collect Tesla’s pieces. They’ve used a device on Nick that hypnotizes him and makes him feel their presence is normal as they raid the attic. A red flag somewhere in the back of Nick’s mind causes him to call Caitlin. She tells him how to get the device away from Jorgenson. This clears Nick’s mind, and he uses one of the Teslanoid Objects to freeze some of the Accelerati and their vehicle. The scientists escape on foot, but not before Nick has frozen Jorgenson’s arm and the man’s pinkie has broken off. Vince and Caitlin arrive, and the three remove the Teslanoid objects from the Accelerati’s defrosting SUV.
Ms. Planck takes Petula to meet Jorgenson in the Accelerati’s secret lair beneath a bowling alley. He gives Petula a device to plant on Nick that will kill power everywhere he goes. She puts it in Nick’s shoe. Later, Petula and the other kids meet in Nick’s attic to decide how to protect the FREE. Mitch suddenly realizes the Accelerati is responsible for getting his dad thrown in prison. Mitch’s dad was accused of simultaneously stealing one penny from every bank in the world with the click of a keystroke. Mitch becomes increasingly vengeful, formulating his own plan to take down the Accelerati. Vince begins to see the kids will eventually need the battery that keeps him alive to make the FREE function properly. He begins plotting to ensure the missing pieces of the machine will never be retrieved.
Nick visits Jorgenson. He says he will give the scientist whatever he wants if Jorgenson will remove whatever is making Nick cause power outages. While Jorgenson’s back is turned, Nick sneaks the tiny power-killing device into the scientist’s food. Jorgenson swallows it and suffers from its effects.
Petula continues to ponder her roles as an Accelerati member and friend of Nick’s. She decides to tell Nick she knows where the Accelerati has hidden the harp. Still not admitting her association with the group, she makes up an explanation for her knowledge and takes the kids to the Accelerati’s lair. There, they battle a few Accelerati members and leave with the harp. As they’re leaving, they notice the sky is growing dark. Mitch is also producing high winds with one of Tesla’s machines to get away from the pursuing Accelerati members. A tornado ensues, as do other natural disasters around the globe.
Back at Nick’s house, the kids add the harp to the FREE. Petula knocks Nick out and removes Vince’s battery. Vince falls down the stairs, landing on Caitlin. Jorgenson climbs out from under the bed, just as he and Petula had planned. She warns Jorgenson the machine doesn’t have all of its pieces, but he believes there are enough there to start it up. Petula demands that she start it up, as the harp had told her she would complete the circuit. She and Jorgenson fight while Nick gets up and starts the machine. The attic begins to rise, levitating above the house. The walls blow off of the attic, and Nick can tell the machine is malfunctioning. Jorgenson begins to fall, and Nick extends a hand to save the man’s life. Nick then sticks his hands into the machine to dismantle it and break the circuit. It is intense and painful, but he succeeds. The attic crashes back onto the house.
Caitlin later visits Nick in the hospital to tell him Mitch has reanimated Vince, and Petula is nowhere to be found. Nick is startled to see Jorgenson, but the man says he won’t kill Nick because Nick saved his life. Caitlin goes to get them soda at the vending machine. When she returns, Nick is gone.
The Accelerati whisk Nick away by plane to a secluded old house in the woods. He meets Jorgenson’s boss, who turns out to be Thomas Edison. He has been kept alive by a wet-cell battery. Edison gripes about Tesla before giving Nick an ultimatum. He says Nick’s dad is in jail for conspiring against the government, and Danny is in foster care. Edison will make these charges go away if Nick will agree to join the Accelerati and help rebuild Tesla’s machine. Nick feels he has no choice but to agree to the terms.