Charlie Thorne and the Lost City

The second installment in the Charlie Thorne series opens with a prologue set in 1835. Charles Darwin, the young English naturalist aboard the HMS Beagle, returns to the ship in Guayaquil, Ecuador, after a mysterious 10-month expedition into the South American interior. He is barely recognizable, emaciated and covered in sores, and urgently orders Captain Robert FitzRoy to set sail before a pursuing mob reaches them. Two men of Incan descent accompany Darwin, carrying a large wooden chest, and Darwin reveals that all 11 crewmen who went with him are dead. When he opens the chest, FitzRoy is horrified, privately considers the contents an affront to God, and resolves to destroy them.

In the present day, 12-year-old Charlie Thorne is living under a false name in Puerto Villamil on Isla Isabela in the Galápagos Islands. Charlie possesses an extraordinarily high IQ, speaks over a dozen languages, and is the only person alive who has memorized Pandora, a dangerous equation discovered by Albert Einstein that reveals how to access the energy inside atoms. After a previous CIA mission ended badly, Charlie faked her death and fled to the islands, keeping a packed emergency bag and a booby-trapped rental house.

Her hiding ends when Esmerelda Castle, a woman from the Charles Darwin Research Station on a neighboring island, appears with a coded message carved by Darwin into the belly shell of a recently deceased giant tortoise. The inscription reads "The Greatest Treasure in Human History" and includes a three-line poem. Charlie deciphers it instantly: "Find the devil's stone in Quito." She conceals the solution because she spots a suspicious man asking locals about her. She opens a propane valve as a booby trap, escapes with Esmerelda, and flies away on Esmerelda's seaplane.

The man is Ivan Spetz, a deep-cover agent for the SVR, Russia's foreign intelligence service. He triggers the explosion, traces the seaplane to the research station, and sends the tortoise code to Russian cryptographers, who crack it quickly. Meanwhile, CIA Director Jamilla Carter receives covert messages from Agent Dante Garcia, Charlie's half brother, confirming he has located Charlie. Only Carter, Dante, and Agent Milana Moon know Charlie is alive.

During the flight, Esmerelda shares her family's obsession with Darwin's hidden treasure. A distant Castello ancestor served on the Beagle and hinted at a hushed-up discovery. Esmerelda's father spent his life pursuing the mystery and on his deathbed made her promise to follow the trail. She spent six years in the Galápagos, aided by her brothers Paolo and Gianni, until the coded shell was found.

In Quito, Charlie traces the legend of the Devil's Stone, a stone from San Francisco Church that was later placed atop the spire of the Basilica of the National Vow. She notices that Esmerelda has a rare genetic condition causing pain to fade almost instantly and deduces her real surname is Castello. Charlie secretly buys a mountain bike as an escape vehicle. On Good Friday, the two climb the Basilica's spire disguised as cucuruchos, purple-robed penitents in the traditional procession. At the top, Charlie finds a stone orb etched with numbers. When she descends, Esmerelda holds her at gunpoint. Charlie drops off the spire using her climbing rope and escapes on the bike.

A harrowing chase through Quito follows, with Ivan in a car and Esmerelda's brothers on foot. Charlie causes Ivan to crash and wipes out in a ravine, where Dante and Milana rescue her. She decodes the spire numbers using a box cipher, a system where pairs of digits correspond to letters. The message reads: "Follow the Napo River east from Coca for ten days until the water turns to blood. Then find the tree built like King's College Chapel." Charlie offers Dante a deal: Help find Darwin's treasure, and she will surrender Pandora. He agrees.

Ivan plants a tracking device on Paolo's phone and lets the Castellos decode the message themselves. All parties converge on the Amazon. Charlie, Dante, and Milana acquire a speedboat and head downriver. The Castellos attack from a rented seaplane, strafing with machine guns. Charlie dives into the river, swims to a passing oil barge, and ignites a crude oil spill with her grandfather's lighter. The explosion destroys the plane. Dante rescues the burned Castellos and deposits them at a nearby oil refinery, where the manager, Oswald "Oz" Crutcher, overhears talk of treasure and decides to follow.

Days later, the team finds a red-water tributary, fulfilling the "water turns to blood" clue. Nearby towers an enormous kapok tree whose massive buttress roots resemble the flying buttresses of a Gothic chapel. They dock at an eco-lodge run by Segundo, a local man whose ancestors have guarded the tree's markings for generations. Segundo shares a legend of a white explorer who traveled upstream to the "Dark Lands" with 11 men and returned with only three, carrying a mysterious chest. Charlie decodes the tree's message: "Follow the red river upstream for a month until you reach a place that looks like the Thames. Then find the altar in the main temple in the city of stone." After they leave, Ivan arrives and threatens Segundo into revealing the decoded message.

During the grueling upriver journey, Charlie reveals her theory: Darwin's treasure is not gold but living evidence of evolution. She believes convergent evolution, the process by which unrelated species independently develop similar traits, produced prehominids in South America: ape-like creatures partway between monkeys and humans, analogous to how apes evolved toward humans in Africa.

They reach a steaming lake resembling the polluted Thames of Darwin's era and discover the lost city on its far shore, consumed by rain forest. Inside a massive temple, they find walls lined with gold and footprints made by a knuckle-walking creature. On the altar, Darwin etched a crude drawing of a prehominid and three words: "They live here." Charlie insists they leave to protect the creatures from exploitation.

Before they can escape, Ivan and Esmerelda force them back at gunpoint. Oz's men also arrive. When a female prehominid emerges from a thunderstorm, Oz shoots at it. The wounded creature howls, and the prehominids launch a coordinated attack, overwhelming Oz's crew. Charlie bandages the creature she names Eve and collects a branch from a shrub whose resin produces curare, a potent paralytic poison. The Castello brothers pursue Charlie but are killed by an anaconda. Ivan tranquilizes the group and loads them onto a Russian military helicopter.

Charlie wakes aboard the helicopter and deploys bullet ants she has been collecting throughout the trip, flicking them onto Ivan and Esmerelda. The excruciating stings incapacitate Ivan. Esmerelda recovers quickly due to her pain condition, but Charlie has scratched her with nails coated in curare, and the poison weakens Esmerelda's muscles. They crash-land at Machu Picchu on the edge of a 1,500-foot gorge. Esmerelda lunges at Charlie with a knife, but Eve knocks Esmerelda into the cockpit. The helicopter tips over the cliff and explodes, killing Ivan and Esmerelda. Eve gives Charlie what looks like a slight smile, then disappears into the ruins.

A week later, Dante finds an email from Charlie on his secure CIA account. She is safe but warns that if anyone reveals the creatures or the city, she will never surrender Pandora. Dante and Milana realize Charlie had hacked his encrypted emails long ago and already knew about Einstein's full list of geniuses who hid discoveries. She had been in the Galápagos deliberately searching for Darwin's first clue, manipulating them rather than the other way around. Taking Charlie's persistent teasing to heart, Dante kisses Milana. Charlie, standing at Iguazu Falls, reviews Einstein's list, settles on Cleopatra, and books a flight to Egypt.