One night in 2023, Erik was searching a social media channel he regularly visited for pornographic content.
After a few seconds of watching a video, it froze.
He realized that the couple watching him enter the room, put down their bags, and later have sex was actually him and his girlfriend.
Three weeks earlier, they had spent the night in a hotel in Shenzhen, a city in southern China, unaware that they were not alone in the room.
Their most intimate moments were recorded by a camera hidden in their hotel room, and the footage became available to thousands of unknown people who signed up for the channel that Eric himself used to watch pornographic content.
Erik (not his real name) was no longer just a viewer of Chinese pornography recorded with spy cameras, but also a victim.
Warning: There are offensive words in the text.
So-called spy camera pornography has existed in China for at least a decade, despite a ban on the production and distribution of pornography in the country.
But in the last few years, the problem has become a frequent topic on social media, where people, especially women, are exchanging tips on how to detect cameras that are the size of an eraser on the tip of a pencil.
Some even started setting up tents in hotel rooms to avoid being filmed.
In April last year, China introduced new regulations in an attempt to curb this phenomenon, requiring hotel owners to regularly check for spy cameras.
However, the threat of secret filming in the privacy of a hotel room has not disappeared.
The BBC World Service has found thousands of recent spy camera footage on multiple websites, recorded in hotel rooms and sold as pornographic content.
Much of this material is advertised on the messaging app and social network Telegram.
Over the course of 18 months, I discovered six different websites and apps advertising on Telegram.
They claim that they collectively have more than 180 spy cameras in hotel rooms that not only recorded, but also live streamed the activities of hotel guests.
I monitored one of these sites regularly for seven months and found content recorded using 54 different cameras, about half of which were always active.
Based on the usual number of guests, the BBC estimates that the spy cameras could have recorded thousands of guests during that period.
Most people probably don't even know it was recorded.
Eric, from Hong Kong, started watching secretly recorded videos as a teenager, and was drawn to the raw nature of the footage.
"What attracted me was the fact that people don't know I'm filming them," says Erik, who is now in his thirties.
"I think traditional pornographic content feels very staged, very fake."
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But, ever since he found a video of himself and his girlfriend "Emily" and experienced what it's like to be on the other side of that chain, such content no longer gives him pleasure.
When he told Emily that their stay at the hotel had been filmed, edited into an hour-long clip and posted on Telegram, she thought he was joking.
But then she saw the footage herself and was humiliated and embarrassed.
Emily was terrified that the footage could be seen by colleagues and family.
The couple hasn't spoken in weeks.
So how does an industry that exploits the intimate sexual relationships of couples who are unaware that they are being recorded by a voyeuristic camera for paying subscribers work, and who is behind it?
One of the most prominent dealers in spy camera pornography that I found was an agent known as "AKA."
I introduced myself as a user and paid for access to one of the live streaming sites he promoted, with a monthly subscription fee of 450 yuan ($65).
When I signed in, I had the option to choose from five different live streams, each showing several hotel rooms, which would appear on the screen as soon as the guest enabled the room's electricity by inserting a card.
It was also possible to rewind the live broadcast and download archived recordings.
AKA advertised the live broadcasts on Telegram, which is banned in China but is often used for illegal activities.
During our investigation, one Telegram channel had as many as 10.000 members.
Libraries of edited live broadcasts from that channel are also available on Telegram for a fixed fee.
I was able to watch more than 6.000 videos in the archive that were made back in 2017.
While watching hotel guests who don't know they're being filmed, AKA subscribers comment on Telegram.
They comment on their appearance, their conversations, and their sexual skills and relationship.
They celebrate when a couple begins sexual intercourse and complain if they turn off the lights and hide in the dark.
Women are regularly described as "sluts", "whores" and "bitches".
By combining several pieces of information from subscribers, social media users, and our own research, we were able to track down a spy camera in a hotel room in Zhengzhou, a city in central China.
Field investigators were able to access the room and found a camera with its lens pointed at the bed, which was hidden in a ventilation unit in the wall and connected to the building's electrical network.
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The hidden camera detector, which is sold online as "mandatory equipment" for hotel guests, did not activate.
The team disabled the spy camera and the news quickly spread on Telegram.
"Junghua [camera name] is down," wrote one subscriber on the main channel run by AKA.
"What a shame; that room has the best sound quality," AKA replied in the chat.
But the complaints turned to celebration when, within hours, AKA announced that a replacement camera had been activated at another hotel.
"That's the speed of... [our live streaming platform]," AKA told his subscribers.
"Impressive, isn't it?"
During our 18-month investigation, we identified about a dozen agents like AKA.
From the conversations they had with subscribers, it was clear that they were working for others, higher up in the supply chain, whom they called "camera owners."
Agents' comments indicated that these people organized the installation of spy cameras and operated live streaming platforms.
In a direct message exchange with AKA, he accidentally shared a screenshot of a message from someone he said was the "camera owner," whose profile name was "Brother Chun."
AKA quickly deleted the message and refused to discuss it, but we were able to contact "Brother Chun" directly.
Despite our evidence that he provided the live streaming site that AKA used, Brother Chun claimed to be just another sales agent, although he did sort of acknowledge that there were others in the supply chain, higher-ranking than people like him.
What is clear is that people who work for this network can make good money.
Based on the number of channel members and subscriptions, the BBC estimates that since last April, AKA alone has earned at least 163.200 yuan ($22.000).
Last year, the average annual salary in China was 43.377 yuan ($6.200), according to the National Bureau of Statistics of China.
China has strict rules on the sale and use of spy cameras, but we found them relatively easy to buy in Huaqiangbei in the Shenzhen area, the country's largest electronics shopping mall.
It is more difficult to obtain accurate data on the number of people who have been tried for pornography recorded with spy cameras.
In recent years, Chinese authorities have released significantly fewer details about these court cases, but the ones we found indicate that the phenomenon is widespread across China - from Jilin province in the north to Guangdong in the far south of the country.
Blu Li, from the Hong Kong-based NGO RainLily, which helps victims remove explicit secretly recorded footage from the internet, says demand for her organization's services is growing, but the work is becoming increasingly difficult.
He says Telegram never responds to the organization's requests to remove content, forcing them to contact group administrators, who are the people selling or sharing pornography recorded with spy cameras and who have little reason to respond.
"We believe that technology companies have a large share of responsibility for solving these problems."
"These companies are not platform-neutral, because their policies shape how content is distributed," says Li.
The BBC also informed Telegram that AKA and Brother Chun, as well as the groups they lead, were sharing pornography recorded with spy cameras through their platform, but Telegram did not respond or take any action.
When we contacted Telegram 10 days later and provided all the findings of the BBC investigation, they responded:
"Sharing pornographic content without consent is expressly prohibited by Telegram's terms of use," they added, adding that the platform "proactively moderates... and accepts reports of [inappropriate content] to remove millions of pieces of harmful content every day."
We presented our findings to both Brother Chun and AKA that they are making money by exploiting hotel guests who are unaware that they are being recorded by spy cameras.
They did not respond, but a few hours later the accounts they used to promote the content on Telegram appear to have been deleted.
However, the site that AKA sold me access to is still live streaming the events in hotel rooms.
Eric and Emily are still traumatized by their experience.
They always wear hats outside so that no one recognizes them and they avoid staying in hotels.
Erik says he no longer uses these Telegram channels to watch pornography, but checks them occasionally because he is afraid the video might resurface.
Additional reporting: Kate Brown, Bridget Wing and Mengyu Dung
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