Isabel Allende’s novel City of the Beasts tells the story of Alex Cold, a fifteen-year-old boy from California who accompanies his journalist grandmother on a life-altering journey through the Amazon.  

The narrative opens with Alex at home in California, angry and frightened over the illness of his mother, who is undergoing cancer treatment. When his mother gets a chance at receiving a promising new treatment in Texas, Alex’s parents send him to stay with his paternal grandmother, the adventurer and travel writer Kate Cold. Kate is about to embark on a trip to the Amazon, on an assignment forInternational Geographic magazine, with the goal of finding and documenting a mysterious, menacing rainforest presence known only as The Beast. The Beast has rarely been sighted but is known to attack humans, and it leaves a terrible smell wherever it goes. Alex reluctantly joins Kate on her expedition, feeling both excited and apprehensive about the enormous change from the life he knows. 

Alex and Kate travel to the Brazilian city of Manaus, where they embark on a journey by boat up the Rio Negro. Joining them are a number of colorful characters with their own motivations for joining the expedition: Ludovic Leblanc is an arrogant anthropologist, Timothy Bruce is a steadfast photographer, and Omayra Torres is a beautiful young doctor hoping to vaccinate native peoples against outside diseases. The group travels up the Rio Negro, experiencing a stunning array of flora and fauna, to arrive in a village called Santa Maria de la Lluvia. There, Alex meets Nadia Santos, a beautiful and intuitive girl with a near-mystical connection to the natural world. Nadia lives with her father,César Santos, who serves as the expedition’s guide, and she introduces Alex to the complicated forces at play in the village and the surrounding region. These include the menacing figures of Mauro Carías, a greedy entrepreneur, and Captain Ariosto, the commander of the village military, who Alex and Nadia overhear plotting to destroy the native peoples for their own gain. Through Nadia, Alex also meets an ancient shaman named Walimai, who warns Alex and Nadia of coming danger in the form of a dark spirit called the Rahakanariwa. Nadia also informs them of the roles they are destined to play in stopping it. Alex is skeptical of Nadia and Walimai’s mysticism, but he begins to change his mind when he meets a caged black jaguar and has a vision of communing with it. Nadia informs Alex that the jaguar is his animal totem and represents his true nature. 

Guided by César Santos and joined by Nadia, the group sets off up the river, to find the Beast, and falls prey to a host of misfortunes, ultimately resulting in their becoming stranded in the jungle. While they wait for help to arrive, the Beast visits their camp and kills one of the soldiers guarding them, terrifying the group and making the immediacy of their danger clear. Shortly thereafter, Alex and Nadia are kidnapped by an elusive tribe of Indians called the People of the Mist, who take them through the jungle and up the face of a waterfall to their hidden home, known as the Eye of the World. The tribe’s chief is injured during the journey and dies soon after their arrival in the village, but before he dies he informs Nadia and Alex that they are destined to help stop the Rahakanariwa from destroying the tribe, echoing Walimai’s earlier prophecy. Alex and Nadia are welcomed by the other members of the tribe and become symbolic members, learning of their true identities as Jaguar and Eagle and beginning to embrace their inner strength. The new chief, Iyomi, names Alex and Nadia chiefs as well; Alex is tasked with negotiating with the outsiders and Nadia is tasked with soothing the vicious Rahakanariwa. 

Accompanied by Walimai, Alex and Nadia set out to fulfill their destinies by visiting the home of the gods, which turns out to be a beautiful, isolated valley inhabited by the Beasts themselves. Alex and Nadia learn that the Beasts are in fact ancient sloth-like creatures who have lived there undisturbed for thousands of years, acting as gods to the People of the Mist by recording the tribe’s history in their prodigiously long memories. Once Alex and Nadia understand that the Beasts have been leaving their valley to attack human outsiders and protect the tribe, they convince the Beasts to stop doing so and state that they themselves will protect the tribe. The Beasts and the visitors share a communal dream in which the dreaded Rahakanariwa breaks free and attacks the tribe, underscoring the importance of Alex and Nadia’s task. Before leaving the valley, Alex and Nadia negotiate with the Beasts for the chance to seek two treasures from the valley: the water of life, which might heal Alex’s mother, and the crystal eggs that Nadia previously saw in a vision. Each of them undertakes a perilous quest and both succeed, taking their prizes with them from the valley. 

When they return to the village, Alex and Nadia discover that the rest of the expedition has arrived via helicopter, along with Carías and Ariosto. Nadia negotiates with Chief Iyomi to convince the tribe to accept vaccinations from Dr. Torres, hoping that doing so will protect the tribe from outside harm. After much debate, Iyomi agrees to Nadia’s request, but after Nadia catches Dr. Torres and Carías professing their love for each other, she and Alex remember their dream in the city of the Beasts and realize that the alleged vaccinations are actually viruses that Carías, Torres, and Ariosto have been using to decimate native populations. Nadia interrupts before the natives receive the vaccines, but her revelation sets off a chain reaction of violence that leaves several Indians and members of the expedition dead, and Carías gravely injured. Although it seems that Ariosto might kill the remaining members of the expedition in order to hide his secret, Nadia and Alex succeed in calling Walimai and the People of the Mist to their aid. The tribe ultimately summons the Beasts to kill Ariosto and stun his soldiers so that the tribe can move the rest of the expedition to safety. The tribe decides to move to a new village within the Eye of the World, in order to forget the conflict in their previous village, and the outsiders depart with promises to protect the tribe from future interference. Alex convinces his grandmother Kate to use her journalism to protect the People of the Mist and make the outside world think that the Beasts are only a myth. 

Back in Santa Maria de la Lluvia, Kate and the anthropologist Leblanc recover sufficient evidence of the crimes of Carías and Torres to bring them to justice. They also plan to start a foundation together to protect the People of the Mist. Nadia reveals to Alex that the crystal eggs are actually diamonds and gives them to him to help fund the foundation. Alex and Nadia reflect on the growth they’ve undergone since meeting and promise to remain best friends.