M's story had been a horrific one - yet how was she to prove it?
When she'd been abducted as a teenager from her home in Vietnam and trafficked into China, my young Hmong friend had been stripped of her clothes, her Vietnamese phone, and her identity.
When she'd been sold as a bride to a Chinese man, she carried no evidence of the past she'd left behind.
To her captors, M was merely another piece of merchandise, one of countless Vietnamese Hmong girls being trafficked into China.
M, however, took it very personally.
For years, M had remained in contact with the Chinese Hmong couple who had sold her to her Chinese "husband". Feigning friendship, she waited and watched for her chance to betray the couple to the authorities.
When his wife was arrested and imprisoned last year, M's Chinese Hmong trafficker had outfoxed the police.
In an act of incredible courage and audacity, M had at last succeeded in acquiring his name and precise location.
What's more, she knew he was currently holding two more trafficked girls in his home. M knew her trafficker could be caught red-handed - and his two most recent victims saved - if only she could convince the police to act quickly.
Yet how was she to convince the police to act at all? How was she to win their support, when she herself was living in China illegally? What evidence could she offer to support her story?
I met with one young trafficked woman who had escaped her Chinese "husband", only to be caught by the authorities while attempting to cross back to Vietnam. For months she had been detained in a crowded cell in southern China while the authorities attempted to verify her identity and provenance.
Another story tells of a trafficked woman who fled her Chinese "husband" only to meet further suffering and exploitation at the hands of the authorities.
Without any legal status, these were the dangers M now faced.
Last year, I made contact with M in China. It was her first real connection in almost three years with a world she thought had forgotten her.
Before we were able to meet in person, M and I spent a great deal of time communicating by phone. She sent me photographs of the strange new world in which she found herself, including pictures of herself, her "husband" and their baby daughter.
In return, I sent M small reminders of the world she'd left behind. I sent M photographs of her family and friends in Vietnam, and of she and P and I. Visible in the images were the typical costumes and settings of M's home in northern Vietnam.
M approached the Chinese police with the photograph she'd taken of her Chinese Hmong trafficker's ID card, revealing his full name and address. She told them of her abduction from Vietnam and sale in China, giving as evidence the photographs I'd sent her, and others of her new life in China.
M's story was accepted. Acting on the information she provided, the police succeeded in arresting her Chinese Hmong trafficker.
After a process lasting weeks, M has been told that the man is expected to serve five years in prison. (His wife was previously sentenced to 2.5 years, M says). It is unclear at this point what has happened with the man's two most recent victims.
M was elated with her success. In her own words:
"I come to take the man, he sell me to my husband... He very mean, he sell everybody... I tell to the policeman, 'He take many Hmong girls coming to sell in China. He not the good man'... I take all my photos what before you send to me. You, me, P, all the Hmong girls. To put in the policeman... The policeman say, 'You are clever'. He say that... And the policeman go to take he."
Though still illegal, the police permitted M to go freely.
For almost four years, there was only one place M truly wanted to go - back to her home and family in Vietnam. In all that time, she had never been so close.
She was almost there - yet M remained without papers, and the border still lay between them.