An excerpt from The Healing Book.

When Allie’s canoe tapped the dock in Iquitos, Peru, she didn’t know which was greater: her exhaustion or her anticipation. After hours on the Amazon River, she was sticky with sweat, and her arms and legs itched and ached in the wake of countless mosquito bites. However, their arrival meant she was that much closer to experiencing a traditional shaman-led ayahuasca ceremony.

Allie dragged herself from her seat and onto dry land. After taking a moment to roll her neck and shoulders, which had become tight from rowing, she hefted her bags onto her back. Then she joined the rest of the group as they followed a guide along a narrow path through dense forest. When they reached an open encampment, she was directed to a private bungalow, where she dropped her bags, and then to a larger hut for dinner.

Entering the hut, Allie and the others took seats around a table made from the cross-section of a tree. She was just getting settled when they were joined by the shaman, who wore a colorful shawl and had his dirty-blond hair pulled back into a bun.

“Welcome, welcome.” He removed a lit cigar from between his lips. “My name is Matteo. I am so glad you’ve come all this way to see us. Please eat! You’ve traveled a long way and must be starving.”

In the dim lighting of a kerosene lamp, the group ate papayas, bananas, and breadfruit while Matteo told them about his healing practice. It centered around the potent ayahuasca brew, which had produced remarkable stories of healing in combination with his traditional ceremony.

Allie was familiar with many of these stories after months of reading about the white man who had left his middle-class life in California years before to treat his depression through shamanistic ritual here in Peru. Years of training had turned Matteo into a powerful healer, some believed, and people visited him from all over the world in search of cures for anything from addiction and asthma to depression and cancer.

As a neurosurgeon, Allie was skeptical, yet emerging research on ayahuasca was compelling. Studies had shown that ayahuasca improved the body’s absorption of serotonin—the “happy hormone.” Knowing this, Allie had tapered her use of SSRIs leading up to her trip lest the ayahuasca lead to serotonin syndrome.

Matteo blew out a plume of smoke. “Ayahuasca means ‘vine of the soul.’ The ayahuasca concoction you will drink during the healing ceremony contains a chemical that will produce visions. These visions will allow you to bypass your mental defenses and access deeper layers of your subconscious, which will help you reorient the way you perceive yourself.”

“Die to the flesh; awaken to the spirit,” someone remarked.

Matteo nodded. “We call it ego death.” The wrinkles in his face lifted. “The ceremony will also allow you to purge any bad spirits that might have attached to you throughout your life. During the ceremony, I’ll protect you from harmful spirits, but you will need to be brave for the shamanistic healing to work.”

Allie raised an eyebrow. “Spirits?”

“People who have passed on but haven’t yet left the earth. There are many: proud spirits, spirits who are envious of our human forms, despondent spirits. Some can be harmful, and I’ll fight those off if they appear. However, not all spirits mean harm. During the ceremony, pay attention to what you see—images of loved ones or strange figures—as they may have some significance.”

Mentioning the healing center—which sat behind the hut they ate in—Matteo instructed them to meet there by nine that night for the ayahuasca ceremony.

After dinner, Allie trudged along a narrow dirt path to her bungalow. She washed her face and lay down on her bed. Exhausted as she was, she didn’t dare close her eyes lest she invite in a rush of unwanted images: the sixty-pound body of her older sister, Vera, writhing on a hospital bed, gasping for breath in her final hours, eyes sunken, skin loose, papery-skinned hands reaching toward Allie in desperation.

A talented engineer and pride of the family, Vera had been destined for her dream job at NASA when she’d been burdened with a mysterious chronic disease that affected the connective tissues and led to severe malnutrition. Allie had tried so hard to work with her sister’s doctors to help diagnose and treat Vera’s disease, but it hadn’t been enough. She even feared all her efforts had somehow complicated matters, leading to Vera’s untimely death.

Right at nine, Allie entered the healing center, not sure what to expect. Everyone else was already present, seated quietly on meditation cushions. Behind them, empty yoga mats splayed out in several rows. Standing at the front of the room, Matteo sang in a language Allie didn’t recognize, and he smiled and nodded to her when she met his gaze. Beside him sat a large barrel that no doubt contained the ayahuasca brew.

A petite man with a soft face, who’d been introduced to them earlier as Matteo’s apprentice, led Allie to a cushion. He collected her cell phone, offering to take pictures if he could. He placed a cup in front of her, as well as a plastic pail for vomit.

“What is he singing?” Allie inquired.

“Songs that call forth the plants’ healing properties,” the apprentice explained. Matteo continued singing as he ladled a thick, brown concoction out of the barrel into cups. He handed the cups to his apprentice. While Matteo only filled most of the cups halfway, the one he filled for Allie was filled to the top.

The apprentice set the cup down in front of Allie and winked. “Those who need the most healing get the most brew.”

Allie’s neighbor eyed her cup. “You must be teeming with demons.”

Demons. Just another word for trauma.

Dustin Grinnell is a writer and author of The Empathy Academy and The Healing Book.