Charlie Thorne and the Last Equation is the first novel in the middle grade adventure series by American author Stuart Gibbs, author of the New York Times bestselling Spy School series. Charlie Thorne and the Last Equation follows 12-year-old genius Charlotte “Charlie” Thorne as she assists the CIA in solving a mysterious equation left behind by Albert Einstein, racing against time to stop a terrorist cell from gaining a devastating weapon. While featuring a globe-hopping adventure that spans from America to Israel and back again, shocking twists, and cinematic action, Charlie Thorne and the Last Equation also thoughtfully explores The Ethical Implications of Scientific Advancement with an underlying tone of girl empowerment.

This study guide uses the 2020 paperback edition published by Simon & Schuster.

Content Warning: This guide and source material depict white supremacist/racist ideologies. In addition, the novel presents racist comments and language, which are replicated in this guide only in direct quotes from the source material.

Plot Summary

As Albert Einstein lies dying in 1955, he deliriously speaks of the mysterious “Pandorabuchse” (3). Following his death, Einstein’s friend Ernst Klein arrives to burn Einstein’s papers per his wishes, hoping to eradicate Pandorabuchse. Before he can finish, however, strange men rush to stop him.

In the present day, Agent Dante Garcia requests permission from CIA Director Carter to bring 12-year-old genius Charlie Thorne in to consult on the Pandora mission. Though Carter does not trust Charlie, a known criminal, she allows Dante and another agent, Milana Moon, to proceed.

Dante and Milana find Charlie in the Colorado mountains, skiing the infamous Deadman’s Drop. With her ability to visualize equations in her head, she survives the landing and skis into Milana, who is waiting for her at the bottom. The agents catch Charlie following a brief chase. On a jet, Dante explains to Charlie that the CIA is searching for an equation hidden by Einstein called Pandora’s Box. This equation would make it easier for anyone to use nuclear power. Knowing Charlie stole $40 million, Dante uses blackmail to force her to help him find Pandora before a terrorist group called The Furies does.

Meanwhile, the Furies and their leader, Alexei Kolyenko, head across the Mediterranean in search of Pandora. Alexei hates immigrants and non-white cultures; fueled by white supremacist ideology, he intends to bomb major cities.

Solving Einstein’s clue, Charlie determines that Pandora is hidden in a book now kept in archives in Jerusalem. However, Charlie knows Dante is hiding something. While they stop to refuel the jet, Charlie demands that Dante tell her the truth. He admits that the Furies have already found and killed one undercover CIA agent, John Russo. During this exchange, Milana realizes that Dante and Charlie are siblings.

They travel to Israel, where two more agents meet them, and head to Einstein’s archives in Jerusalem to retrieve the book. Charlie realizes the Furies have beaten them there. One Fury steals the book, but Charlie tackles him and retrieves it. Charlie finds a piece of paper hidden in the book but rather than Pandora, it is another clue to Pandora’s location. Then, Charlie and the others go to a CIA safe house. Charlie tries to escape, hoping to protect Pandora from the Furies and the CIA, but Dante catches her. Back in the safe house, the Furies kill the Jerusalem agents and capture the rest. Alexei takes the clue, but Charlie outsmarts him, allowing her and Milana to escape.

Charlie and Milana hide in a church while Dante stays behind. Charlie realizes that John Russo, the agent believed dead, secretly switched sides. John is the true mastermind and now has the clue to Pandora’s location. In the church, Charlie deciphers the clue from memory. Then the Mossad, Israel’s intelligence agency, led by Agent Isaac Semel, arrests them. However, Dante rescues them, and they escape.

Semel orders Mossad agents to block the exits out of the country, but Charlie uses her stolen money to charter a private jet out of Israel. The Furies nearly catch them at the airport, but they escape amid a fuel tank explosion. The Mossad arrests the Furies, and Semel uses satellites to track where Charlie’s jet is going.

Charlie believes Pandora is hidden in the Mount Wilson Observatory in the mountains near Los Angeles. During the flight, Charlie and Dante argue over whether they should give Pandora to the CIA or destroy it. Dante believes the US government can be trusted, but Charlie disagrees. John lands in Los Angeles, but Charlie and the others reach the observatory first. Meanwhile, Semel calls retired Mossad agents in California to track down Charlie.

Everyone converges at the observatory, where Charlie finds Pandora. Before she can read it, Milana demands Pandora, threatening her with a gun. To escape, Charlie causes a small explosion and runs. John chases her. Dante confronts the retired Mossad agents and offers to give them Pandora if they help him save Charlie.

Charlie runs until she is trapped on a cliff. John tries to kill her but accidentally shoots a propane tank, causing a massive fire. Dante tries to rush through the fire but cannot reach Charlie. The explosion slams John into a tree, breaking his back and killing him. Charlie, cut off by the fire, reads Pandora before losing the paper in the flames. Now, Pandora exists only in her head. Metal debris lands near her, and she uses it to snowboard down the cliffside.

After the fire, CIA agents swarm the observatory to search for Charlie and interrogate Dante and Milana. Though the CIA concludes that Charlie did not survive the fire, Dante and Milana see snowboard tracks in the snow and know she escaped.