In the grey gloom of first light it looks like a pile of rubbish - a clutter of cardboard and cloth on a damp pavement.
There is a loud clunk, as the wheels of a city bus lurch through a nearby pothole. Then a small hand reaches out from the middle of the heap, and tugs at a black plastic bag.
I don't think I have a bright future
19-year-old Musa
It's 0600 and 11-year-old Eric Omondi is waking up. He's usually the first. Some of the others have sniffed solvent the night before, to try to take the edge off the cold. Eric doesn't like the solvent - it makes his chest hurt.
There are four boys in all, huddled under their cardboard blankets on the edge of Africa's largest slum.
Eventually the others get up. Twelve-year-old Evans, John who's 13, and the oldest Musa - who's just turned 19.
The boys leave their bedding where it is. It'll probably be stolen during the day - but they've got nowhere else to put it, and they need to start work.
Work
It's about half an hour's walk to Adam's Arcade - a cluster of shops on Nairobi's Ngong road. The boys aren't allowed inside - they'd be chased away by the security guards.
But they can beg nearby, and sometimes people need bags carrying. There's also a place on the other side of the road where they can sit and shell peas for a local businessman - who pays them 20 shillings - about 30 US cents - for a full bag.
Eric arrives at the Arcade wearing everything he owns. Two t-shirts, a pair of green and red shorts, and a battered set of flip-flops. He's eaten nothing since yesterday afternoon.
So he stands near the road, asking for money from the morning commuters - as they squeeze on board mini-buses bound for the city centre.
Someone gives him five shillings. Eric slips it into his grubby shorts and gives his nose a good pick.
Alone
An hour later, all four boys are sitting on a patch of grass behind the arcade, sipping steaming porridge out of plastic mugs. They seem to have got used to me tagging along.
Stealing could see you lynched in minutes
Eric is holding an old football. "It has a hole," he says, squeezing the leather.
"It belongs to us four - we share it. There's a businessman across the road who locks it up for us at night in his shed." Clothes apart - it is their one and only possession.
The boys were all born in the nearby slum. A cramped and filthy squatters camp called Kibera. Home to some 800,000 people - who can't afford to stay anywhere else.
At least half the population of Nairobi live in Kibera and other nearby slums - hidden away like a dirty secret along railway embankments, and beside rubbish dumps.
Eric ran away from home in December, when tribal violence erupted in the slum. He got separated from his family and hasn't seen them since.
Evans left home when his mother died, and his father simply drifted away. John says he was chased out by his mother. Although now he thinks she was actually his step-mother.
"She was bad," he says matter-of-factly.
Future
Musa, the oldest boy, has been on the street for longer than he can remember. He's spent time in a juvenile detention centre in Nairobi.
"I was lucky," he says. "I was not raped."
He'd like to get a proper job, but none of the boys have identity cards, which means the police can round them up whenever they like.
"I don't think I have a bright future," says Musa solemnly.
They all hate the police. When we talk about jobs - that's the one thing they don't want to be.
"All they to is take bribes and beat people," Musa mutters. Although to be fair, the police here earn so little, that it would be absurd to expect them not to demand bribes.
Eric, who had been dozing, stirs and sits up - looking around at his friends, and the potholed street outside Adams Arcade.
Quietly, he says "I think maybe we'll live like this forever."
Vigilantes
Eric is in a good mood. He's already earned 30 shillings today.
He can afford dinner, and then maybe an action movie in one of the crowded video shacks on the edge of the slum.
Without ID cards jobs are hard to secure
A shower costs five bob (shillings). Eric always tries to spend what he's earned. Otherwise someone will just steal it from him in the night.
"There's a big boy called Marcus," he says. "He's a nightmare. He terrorises all of us."
Eric has tried stealing for himself. So have the others. A mango from a stall. A few shillings from a commuter. But it's a very, very risky business.
In Nairobi, in fact anywhere in Kenya, a lynch mob can form in a matter of seconds. The reflex action of a poor community with no faith in the police or the courts.
"I saw one boy I know getting lynched," Eric says. He starts acting out the scene. Showing how the crowd put a car tyre round his neck and set fire to him with petrol.
In the evenings, private vigilante groups patrol the slums, looking for troublemakers. Musa saw one group in action last week. "They'll burn you if you steal one shilling," he says.
And with that, the four boys start wandering back towards Kibera.
An orange sun is already low on the horizon. Just above it, a row of black clouds has formed along the edge of the Rift Valley - half an hour's drive to the west.
Together
The boys are laughing now - kicking a stone instead of their punctured football. And it makes me smile to think that these four dirty, hungry, lonely humans are still children at heart - still able to have fun.
Nairobi is full of street-kids who have lost that instinct. The dead-eyed zombies who patrol the roundabouts down town.
Ten-year-olds with plastic solvent bottles wedged between their teeth, brandishing balls of human excrement - ready to thrust them into an open car window - to force the driver to pay up.
A little later, Eric and his friends stop to pick up scraps of cardboard and coal sacks - tonight's sleeping bags. Later, when it's dark, they'll return to their usual spot on the pavement.
They pay five shillings a night to a watchman who guards the area. There's normally some iron sheeting they can use to shelter from the rain.
By ten o'clock on a weeknight, the slums are quiet. A few campfires flicker in the darkness.
Under a starless sky, Eric, Musa, Evans and John arrange their bedding and huddle down on the cold roadside. A familiar routine. John and Musa on the outside - the two younger boys sandwiched together in the middle.