As dozens of curious onlookers watch in amazement, the Vietnamese spirit medium dances in a trance, attacking invisible enemies with a sword as drums beat and musicians chant.
Civil servant by day and practitioner of traditional spiritual possession rituals when the mood takes her, Nguyen Thi Hoa is clad in a richly embroidered red robe as she performs a Len Dong ceremony at a private Hanoi temple.
"I have no idea what I've been doing," Hoa told AFP after the five-hour performance, which involved at least 15 costume changes.
"Could you tell me what I told you to do?" Hoa, who is not a professional Len Dong shaman and only undertakes the rituals when the spirits move her, asked friends who had watched the entire performance.
Len Dong, which uses musical invocations to lure spirits to possess mediums and communicate with others, has been performed in Vietnam for centuries.
Practitioners and attendees -- people can donate to help cover the costs of a Len Dong performance without having to directly participate -- usually turn to the ancient ritual to ease stress or hoping for help from the spirits with romantic or professional problems.
For decades, Len Dong was restricted by French colonial and Vietnamese communist leaders, but the tradition is enjoying a flurry of popularity since restrictions were relaxed a decade or so ago -- and some say it is a useful vent for stressed citizens.
- Old cure for new ills? -
Six years ago, Hoa began suffering from insomnia, lack of appetite and tiredness. Conventional doctors could not rid her of her ills.
On the advice of a friend, she visited a Len Dong practitioner, who told her to try performing the spirit possession ritual herself.
"To my surprise, my health started improving at once," she said, adding that she started seeing positive changes at work as well.
Len Dong is an ancient Vietnamese custom which involves "calling the spirits of the dead into the bodies of the living to connect past and present," one of the main research books on the topic says.
Musicians play traditional songs to help the shaman enter a trance. Multiple assistants help the shaman to change costumes or prepare offerings -- from chickens to "ChocoPie" snack cakes -- for the altar.
During the ceremony -- an auspicious date for the event is carefully picked in advance by the shaman -- the practitioner will seemingly drift in and out of a trance, singing, chanting and dancing to the minimalist, rhythmic music.
"It's not just the insane dancing of people who have lost their dignity," said cultural researcher Ngo Duc Thinh.
The practise of Len Dong can help people under intense stress or suffering from low-level psychological disorders, Thinh, a renowned professor of Vietnamese culture at a top state research institute, said.
"They practice Len Dong to rid themselves of their problems and return to their normal life," the professor, who has spent more than three decades studying Len Dong, told AFP.
"As society develops, spiritual pressures multiply. Stress becomes more serious -- and this creates more chances for Len Dong," according to Thinh.
- Social stigma -
Hoa practices Len Dong at least twice a year.
"I don't dare tell my mother as she would say I was crazy," said the bureaucrat, who spends around 40 million dong (nearly $2,000) to put on each performance.
Her work colleagues, mostly communist party members, are also not aware of her Len Dong practice -- the ritual has at times been considered heresy, and was totally banned until the 1980s by the communists, although rituals continued in secret.
"I received several warnings from police, asking me to stop my practice," said a professional Len Dong practitioner, speaking on condition of anonymity about that period of time.
Even now, practicing Len Dong can carry a government fine of around $250 which aims to prevent private for-profit practitioners rather than genuine Len Dong devotees like Hoa.
"The government tried to ban it, but they in fact have failed. It's impossible to ban Len Dong," researcher Thinh said.
But it might be necessary to regulate it, some experts say.
Len Dong practitioners usually offer their services at temples between Vietnam's lunar new year -- usually around late January -- to the end of the third lunar month in April.
Since restrictions on the practice were lifted, business is booming and some newly wealthy Vietnamese are willing to pay up to $50,000 for a Len Dong service.
The trouble is, it is hard for people to tell the difference between genuine Len Dong practitioners and con artists.
"Several practitioners, who have only some ability, have used that to cheat people for money," one practitioner told AFP.
"That makes people confused -- they can't differentiate between real and fake Len Dong."