In a tense corner of a dangerous place, we heard voices rising in song - this was the congregation of Saint Temple of Olivier - a church buried deep in the heart of Cite Soleil.
Orla Guerin reports on violence in Haiti's slums
We followed the sound down a warren of narrow alleyways and found a group of women holding an open-air service outside their damaged church.
They have been here continuously since the earthquake struck, hoping their voices will make enough noise to keep the much-feared local gangs at bay.
"There is no water, no food, nothing," said Madame Elote Pierre, the pastor's wife. "When it's night time, it's even more scary. We have to band together for safety. We stay together, praying. We don't sleep."
Some of the congregation have lost their homes, others are too afraid to return to theirs - they fear being raped, if they are found alone. Madame Pierre has lived in Cite Soleil since 1969, and says things have never been worse.
The quake damaged many of the homes of those who live in Cite Soleil
"The situation has never been easy for us," she said.
"But this is the most difficult moment, and the most dangerous. We have had no aid from anyone, and there's no-one to protect us. Our only protection is from God," she said, raising her arms to the sky.
Since the earthquake there are new dangers in Haiti's most notorious slum. The earthquake has created a security vacuum across the capital.
And more than 4,000 prisoners escaped from the ruins of the capital's main jail.
They have come back home to Cite Soleil, according to the dapper local prosecutor, Evens Leveque - a man who often travels with armed guards.
We found him rushing to a meeting with the Cite Soleil police chief, to discuss a shoot-out the night before.
There is no death penalty in Haiti. When citizens catch one of those bandits they are supposed to hold them and call the police, not lynch them. As a judge I know it is unjust and illegal
Evens Leveque Local prosecutor
"The situation is disastrous," he said. "The prisoners came back here with guns in their hands to terrorise the population. But we, as the local authorities, are not going to let that happen."
Having put the gangs behind bars once, he intends to do it again. "We have received orders," he says. "And we'll do it, whether it takes one or two months, or one or two years, unless they have run off somewhere else, or escaped to the countryside."
In the meantime, he says, some of the local population have taken matters into their own hands, lynching gang members in the streets.
"There is no death penalty in Haiti. When citizens catch one of those bandits they are supposed to hold them and call the police, not lynch them. As a judge I know it is unjust and illegal."
But he also knows that many in the slum have lost faith in Haitian justice.
"When people are arrested, sometimes they are free weeks afterwards because the judicial system in Haiti is weak, and our prisons are not adequate," he says.
Lying in his bed in a nearby hospital, Brine Cedernier knows only too well about the gun law on the streets. Half his stomach is covered by dressings applied to his bullet wounds.
His nephew, Rony, sits by his bedside, gently wiped the perspiration from his brow. Until two days ago, Brine supported them both, by providing lifts on his motorbike.
Then he was attacked in the neighbouring slum.
"I was on my motorbike and three guys came," he says. "They told me to kneel down. They took the bike and shot me - twice. Since the earthquake, the gangs are stealing and looting and killing people."
Eighteen-year-old Rony looks away, with tears streaming down his face.
Having already lost his father in the earthquake, he cannot bear the thought of losing his uncle.
On the streets of the seaside slum, gun law is the only law
"He's the only one I have left who loves me," he said. "He's all I have."
Brine is being treated by staff from Medecins Sans Frontieres.
They have returned to the local hospital in Cite Soleil, where they have been based in previous crises. MSF veterans here say they are not hearing as much gunfire as they did in the past.
But they are treating two to three shooting victims a day, and they have been busy with births, amputations, and some machete wounds from looting.
Some food aid is getting through to the slum. We saw people waiting patiently for aid in long orderly queues, under the watchful eye of United Nations troops.
But we saw no sign of the police during our visit - except in the courtyard of their headquarters. Just across the road, there is a bullet-riddled ruin - a symbol of the slum.
Back outside the Church of Saint Temple of Olivier, the faithful say they will continue their vigil.
"We have to stay here together, and keep praying," said Madame Pierre. "We can't risk separating. We pray to God to see the next day, and we pray not to be a victim."
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