In the fourth installment of the New York Times bestselling Charlie Thorne series—which #1 New York Times bestselling author Chris Grabenstein called “a real page-burner”—Charlie searches for Isaac Newton’s secret treasure across Europe and Australia. Charlie Thorne is a genius. Charlie Thorne is fearless. Charlie Thorne may have finally met her match. Charlie Thorne is used to being on the run. Ever since she was recruited by the CIA to track down Einstein’s most dangerous equation, Charlie and former CIA agents, Dante Garcia and Milana Moon, have traveled around the world to prevent history’s greatest discoveries from falling into the wrong hands. But after beating others to the secrets hidden by Einstein, Darwin, and Cleopatra, they find they are not the only ones searching for an immensely powerful discovery of Isaac Newton’s. From a chase over the rooftops of Cambridge University to scaling the Sydney Harbour Bridge to skirting a volcanic eruption, Charlie will need to think one step ahead of her opponents to follow Newton’s trail of devious clues and keep herself out of the hands of the many enemies who are hot on her tail.

“Fast-paced, smart, and action-packed...a real page-burner.” —Chris Grabenstein, #1 New York Times bestselling author of the Mr. Lemoncello’s Library series From New York Times bestselling author Stuart Gibbs comes the first novel in a thrilling new series about the world’s youngest and smartest genius who’s forced to use her unbelievable code-breaking skills to outsmart Einstein. Charlie Thorne is a genius. Charlie Thorne is a thief. Charlie Thorne isn’t old enough to drive. And now it’s up to her to save the world… Decades ago, Albert Einstein devised an equation that could benefit all life on earth—or destroy it. Fearing what would happen if the equation fell into the wrong hands, he hid it. But now, a diabolical group known as the Furies are closing in on its location. In desperation, a team of CIA agents drags Charlie into the hunt, needing her brilliance to find it first—even though this means placing her life in grave danger. In a breakneck adventure that spans the globe, Charlie must crack a complex code created by Einstein himself, struggle to survive in a world where no one can be trusted, and fight to keep the last equation safe once and for all.

After tracking down incredible discoveries by Einstein and Darwin, Charlie is back. This time, the great ruler Cleopatra has left behind an extremely valuable and powerful treasure, its location encoded on an ancient stone tablet. In a breathless adventure that takes her across the globe, Charlie must fight for her life against ruthless enemies, match wits with Cleopatra, and solve the two-thousand-year-old mystery to prevent the most powerful treasure of the ancient world from falling into the wrong hands.

In this sequel to the New York Times bestselling Charlie Thorne and the Last Equation—which #1 New York Times bestselling author Chris Grabenstein called “a real page-burner”—Charlie searches for Charles Darwin’s hidden treasure in South America. Charlie Thorne is a genius. Charlie Thorne is a fugitive. Charlie Thorne isn’t even thirteen. After saving the world, Charlie is ready to take it easy in the Galapagos Islands. That is, until she’s approached by the mysterious Esmeralda Castle, who has a code she knows only Charlie can decipher. In 1835, Charles Darwin diverted his ship’s journey so he could spend ten months in South America on a secret solo expedition. When he returned, he carried a treasure that inspired both awe and terror in his crew. Afterward, it vanished, never to be seen again… But Darwin left a trail of clues behind for those brave and clever enough to search for it. Enter Charlie Thorne. In a daring adventure that takes her across South America, Charlie must crack Darwin’s 200-year-old clues to track down his mysterious discovery—and stay ahead of the formidable lineup of enemies who are hot on her tail. When an ancient hidden treasure is at stake, people will do anything to find it first. Charlie may be a genius, but is she smart enough to know who she can trust?

Charlie Thorne, along with former agents Dante Garcia and Milana Moon, race to find an immensely powerful discovery of Isaac Newton's and face challenges and enemies along the way.

Loyalty is tested in this second book in the thrilling time travel adventure trilogy from New York Times bestselling Charlie Thorne and Spy School author Stuart Gibbs. Having assumed the identity of a young D’Artagnan, Greg Rich is beginning to get the hang of things in 1615 Paris. But he hasn’t figured out how to get home yet. Or how to defeat the dangerous Michel Dinicoeur, who has made it his mission to destroy Greg, Athos, Aramis, and Porthos. When Dinicoeur escapes the Bastille and flees to Spain, the Musketeers charge after him, only to be ambushed. Someone is anticipating their every move. Could there be a traitor in their midst? If the Musketeers can’t trust each other, who can they trust? It’s “all for one and one for all” . . . isn’t it? And don’t miss the action-packed finale, The Last Musketeer #3: Double Cross.

When Charlie's classmate Anthem mysteriously disappears after bringing a supposed space rock to show-and-tell, the Whiz Kids trace his steps to his eerily empty house, where it becomes clear that Anthem and his father are involved in something much bigger than a lost rock.