The psychedelic powers of a traditional Amazonian plant medicine called ayahuasca are attracting more and more tourists. It's said to bring spiritual enlightenment and to help with addiction, depression and trauma. But a string of allegations suggests there's a darker side to the ayahuasca scene.
Warning: this article contains details of alleged sexual assaults
Rebekah first tried ayahuasca on a "complete whim" when she was travelling in Peru in 2015.
"I thought it sounded interesting and I thought I might as well give it a try," says Rebekah, a New Zealander in her 20s who asked the BBC not to use her surname. "So I found a retreat centre that I felt was good and I just went for it and it was amazing."
Ayahuasca can induce visions of things like serpents, palaces, and alien beings - and bring up long-forgotten memories. Like many who've drunk the brew, Rebekah has a wide-eyed distant look as she reminisces about the experience.
"It was like being guided very gently and very kindly through some really awful experiences that I'd had in the past," Rebekah says. "And returning back home after that, I felt like my relationships were a lot stronger. I felt it was a lot easier to share and receive love.
"They do say that ayahuasca is like 20 years of psychotherapy. And I completely believe that."
Ayahuasca is usually taken in ceremonies at night, led by a healer - sometimes called a shaman. He or she will drink the sticky brown liquid - a brew of two Amazonian plants - then dole out helpings to the participants.
It's been used by tribes in the Amazon region for centuries but now there's a boom in what's become known as "ayahuasca tourism", with ever more specialist retreat centres opening. Travellers often come for help dealing with mental health problems - and a growing body of scientific research suggests ayahuasca could be an effective treatment.
About half an hour or so into a ceremony, the medicine takes its effect and the healer will start singing sacred chants, known as icaros, which guide the participants through their visions. Drinkers usually "purge" during ceremonies too, vomiting and sometimes getting diarrhoea as well.
When Rebekah went on her first ayahuasca retreat, she was the only single woman there and noticed that the male healer was paying her special attention.
"How he treated me was very different, which I didn't find suspicious at the time. But upon reflection, now I do."
A year later, by now a more experienced ayahuasca drinker, Rebekah returned to the same retreat in Peru. The same healer was leading the ceremonies.
Once again, she says, she was treated differently from everyone else. There was a lot of flattery. Then the healer began confiding in Rebekah.
"He constantly told me that he had a lot of troubles," she says, "and he said he was having problems with his wife, that he wasn't sexually fulfilled, and that I was the one who was able to cure him of that."
Rebekah was 20 at the time; the healer in his 50s.
"He also promised me a lot of spiritual advancement or a lot of spiritual power, if we had a relationship - while his wife was down the road."
Find out more
- Listn to Simon Maybin and Josephine Casserly's documentary Ayahuasca: Fear and Healing in the Amazon on BBC Sounds
Rebekah says the healer sexually abused her, coercing her into sexual acts.
"It's disgusting," she says. "Because he was a shaman, I thought he had moral superiority in a sense and I trusted him."
After she was abused, Rebekah left the centre - and the country: "I booked a flight and got the hell out of there."
She was left with a tangle of painful emotions: "Disgust, repulsion, betrayal - confusion, as well as to why a guide would do this, why a teacher would do this and why they would exploit their power like that."
Rebekah's alleged abuser is still the head shaman at his centre - which gets five-star ratings on review sites.
"He is still there," Rebekah says, clearly deeply angered by the situation. Her hands are visibly shaking. "There are other centres that I know of as well that are still operating. There've been multiple women that have been sexually abused in these centres."
Experiences of sexual abuse seem to be widespread in this world. We've heard numerous allegations against numerous healers and read many testimonies of sexual abuse on online forums.
One name that comes up repeatedly is Guillermo Arévalo, a well-known healer who's been honoured by the Peruvian Congress for his work on sustainable development.
"He came to Canada many times," says a woman in her 40s whom we're calling Anna.
"It was quite lucrative - big ceremonies. They'd fill up fast, people paying C$300 (£175) to come and sit with Guillermo. He had kind of a status. It was an honour to sit in ceremony with him."
Anna, who had long been interested in alternative medicine, hoped ayahuasca might help her deal with her addiction to heroin.
At first, she was impressed by Arévalo.
"Like a lot of people, you're flabbergasted by the man's presence and power and ability to lead the ceremony - it's quite profound," she says. "The chanting. He is a good healer."
But a ceremony about seven years ago dramatically changed Anna's opinion.
"It was completely pitch black, the room had no windows. There were a lot of people.
"I was under the effects of the medicine. When you're under the effects there's lots of different sounds. People are crying, verbalising things that make no sense at all, purging or moaning.
"Even if I had been able to say something, nobody would respond."
Anna was having a difficult time. She recalls lying down, moaning and groaning. "Guillermo came and he sat with me and at first it was a sense of relief because I think I'm going to get some help," she says.
"He started to chant to me and put his hands on my stomach over my clothing which is normal. And then he put his hands down my pants. And there's this sense of feeling frozen. I lay there in fear and then he put his hands up my shirt and felt around my breasts."
She remembers thinking: "'What the heck was that all about?' Just a sense of disbelief and confusion."
It's taken six years for Anna to feel able to speak out about what happened to her.
"Women are conditioned to accept this behaviour. For myself, coming from a history of addiction - and I've had abusive relationships with men that I've tolerated in my life - and a history of childhood sexual abuse, there's a sense of familiarity there, of normalcy.
"And also this weird co-dependent relationship for me where the medicine was helping me so I didn't want to speak up because I was afraid I would be ostracised from the community and then I would be kind of cut off from the medicine."
Risks and benefits?
While preliminary scientific studies have suggested that ayahuasca could have therapeutic benefits, it contains DMT, which is illegal in the UK, and there are potential risks.
A 2015 report found six volunteers with depression showed a decrease in symptoms after taking it. A separate study two years later indicated that it held promise as a treatment for eating disorders. Psychologists have also speculated that it could help those with PTSD.
The Foreign and Commonwealth Office warns that some people have "suffered serious illnesses and in some cases death" after taking part in ayahuasca ceremonies. It points out that retreats are typically some distance from populated areas and that while some have basic medical facilities, others do not.
Around the same time, a group calling themselves Ayahuasca Community Awareness Canada - which included senior academics - put their names to a letter about Arévalo's behaviour and circulated it within the ayahuasca scene. The letter-writers say they took action because of the number of complaints made against the healer, citing reports of non-consensual or inappropriate sexual behaviour.
When further named signatories were added to the letter in 2015 and it was made public, Arévalo stopped visiting Canada to lead ayahuasca ceremonies.
But when we track him down it seems he's been active all around the world in the intervening years and is now based at a retreat centre in Peru. The place used to be called Anaconda but when we're there has its first group of foreign guests under a new name, Bena Shinan.
They're milling around in a dining room behind us when we put the allegations of sexual abuse to Arévalo, a slight 71-year-old with silver hair and gold teeth.
"I don't accept the allegations because they're not true," he says firmly. "Because sometimes people just imagine these things."
He says he's heard about the letter by members of the Canadian ayahuasca community, but has never read it.
"It doesn't interest me because the allegations aren't true," he says. "It doesn't bother me because I don't think an allegation's going to kill me."
The claims against him, he says, are "the imaginings of the unwell person".
"When you touch someone who's been abused or raped, they think you're the same. That's what happens. That's how I make sense of it."
When we put Anna's specific allegation to him, he says he doesn't remember ever touching a patient during a ceremony in Canada, saying she too must have imagined it.
"What else is he going to do other than just lie and deny it," Anna responds. "Otherwise he would have to step up and take responsibility and be accountable for the way he has acted."
What about his claim that she just imagined the sexual assault?
"It sounds like gaslighting to me, really," she says. "That's what it feels like."
Although Arévalo denies having sexually abused anyone, he does admit that healers working under him have had sex with "unwell people".
He says he no longer works with those healers, but that in some cases it was the patients who initiated the relationships.
"Western women, when they come, they're also seeking out healers," he says.
Anna's experience with ayahuasca and abuse doesn't end with Guillermo Arévalo. Despite her experiences with him, she didn't want to give up the benefits she received from the brew and continued taking it under the guidance of other healers.
She says that in 2014 she was raped in ayahuasca ceremonies in Peru by a healer who is a member of Arévalo's extended family.
She says again she "just froze" and "let him do whatever he wanted to me".
"I think he probably raped me four or five times and I noticed he was doing it to other people."
Afterwards, Anna says she was in shock. She doesn't remember much about that period of her life.
"I started to develop symptoms of psychosis and ended up relapsing and becoming addicted to fentanyl and overdosed and almost died. I think I really blamed myself for a long time - why I couldn't say no, why I couldn't move, why I let him do those things. Those were the things that were going through my mind."
We've spoken to another guest who was at the same retreat as Anna, who says the healer was later sacked from the centre, because of allegations made by other clients. We're not naming him because, despite our best efforts, we haven't been able to reach him to give him the chance to respond to the allegations.
Emily Sinclair, a British doctoral student researching ayahuasca, is part of a group trying to raise awareness about the problem of sexual abuse in the ayahuasca world.
Working with the Chacruna Institute, an organisation set up to share research on plant medicines and psychedelics, Sinclair helped put together the Ayahuasca Community Guide for the Awareness of Sexual Abuse.
The guidelines highlight typical scenarios in which abuse happens. They also encourage people to drink with trusted companions and to research retreats by checking out review websites before they visit.
Sinclair has been distributing the little green booklet to cafes, tourism offices and ayahuasca centres in the Iquitos area of Peru, known as the hub of ayahuasca tourism.
"A lot of abuse we've found occurs in the context of individual healings where a woman might be asked to remove her clothes unnecessarily," she says. "And when she's in this unfamiliar context, she doesn't know if that's normal or not."
Sinclair points out that it's not just indigenous healers abusing Westerners. "Abuse happens across cultures and within them," she says.
"But one of the big problems is that a lot of people who come here romanticise shamans. So we put them on a pedestal. And it's very easy for that image to be taken advantage of.
"There's also assumptions that some of the people here may have about Western women and culture."
Some of the red flags Sinclair warns people to watch out for echo Rebekah's experience.
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"If he's overly touchy with you, he tells you his wife doesn't mind him having sex with other women, he encourages pacts of silence and secrecy between you, he says he wants to teach you 'love magic'. This kind of thing. And also that having sex with them will increase their power and energy. These are all things that have been reported to us as being said to women in this context."
Those affected by sexual abuse understandably find it difficult to talk about openly. On top of that, there's a strong sense within the ayahuasca world that any kind of negative publicity could result in government intervention, which creates an additional pressure to stay silent.
But Rebekah and Anna are speaking out because they hope it will prevent other women being abused.
"I think the only thing we can do is just speak out about it and talk about it," Rebekah says, "make sure people know that it's happening."
Rebekah says that after she was abused there's been "a lot of sadness and a lot of therapy".
It's been hard work for her to trust a healer again, but now she's back in Peru, taking ayahuasca and researching her master's thesis on indigenous medicine.
"Regardless of everything that happened, obviously ayahuasca's great," Rebekah laughs, "because I keep going back to it."