"It was late, 11.35 at night as I walked home when he came at me. I dodged his first swing with the machete, but he hit me here with the bottle," says the 18-year-old, touching the right side of her neck and wincing as if the pain lingered even now.
Born and brought up in the Korogocho and Kariobangi districts, in the north-east of Nairobi, the Kenyan capital, Catherine has spent her entire life living in the shadow of fear, grinding poverty and a squalor that beggars belief.
As she nears her 19th birthday, this young, articulate woman has lost count of the times she has been subjected to violence and confronted with threats of gang rape.
This, in part, accounts for why the neighbourhoods in which she has grown up have acquired the dubious reputation of being among the most violent slums in Africa.
For so many slum dwellers caught in the grip of such places, they often represent life's last stop. To put this another way, in Nairobi's slums you can't fall any further, short of being destitute or dead.
Simply physically navigating these urban hell-holes is like steering your way through a minefield of filth. After a while you give up caring what you may be stepping on: human faeces, raw sewage, dead rats.
In the Swahili language the very meaning of the word Korogocho says it all - "crowded shoulder to shoulder".
So crammed together are the corrugated tin-and-wood shanties in Korogocho and other sprawling Nairobi slums that the alleyways are no more than the width of a coffin. For those entombed in these confines that is precisely what their neighbourhoods feel like - coffins.
Many die young here. Those children who make it past infancy usually face a grim life. Perhaps for this reason Catherine, by her own admission, has been "no angel".
Although the eldest of five children, she was barely into her teens when her father died, leaving Catherine's mother, sister and two brothers dependent on her to survive.
As a youngster she scavenged in the Dandora dump site, a giant mountain of garbage that accumulates from the cast-off waste of Nairobi's four million inhabitants.
On and off for three years Catherine picked scraps from Dandora's canyons of stinking rubbish. Here, rotting food and, hospital waste, leaking toxic chemical containers, discarded foetuses and the occasional dumped corpse, usually victims of gang turf wars, lie in a giant rotting rug.
But Catherine's scavenging for the recycling gangs could never provide her family with enough money to eat and it was only a matter of time before she found herself sucked into another gang culture that led to her peddling "coke and liquid bang" - heroin - on the orders of her brutally controlling drug-gang overseers.
This squalid, violent world that so many children today inhabit, as Catherine did growing up, is a part of Nairobi few tourists see. Its existence stands in stark contrast to the manicured lawns and high security walls of the city's Upperhill district that houses among many other diplomatic missions, the British High Commission.
It was here last Sunday, on a balmy night, that invited guests mingled under marquees sipping champagne.
They had come from around the world, though most were Kenyans and expatriate Britons who had been promised a Scottish theme to a reception that would see the arrival of the Queen's Baton Relay and chime with the welcome they can expect from the host nation of this year's Commonwealth Games in Glasgow.
On the face of it, Nairobi's slum dwellers and this grand occasion appear to have little in common. But look again, and the power of sport to transform the lives of so many disadvantaged children within the Commonwealth Of Nations becomes startlingly apparent by the example being set in Kenya, a country where more than half the population is under 18.
Kenyan track and field athletics legend Kip Keino made the case for sport's ability to empower youth after he and British High Commissioner Christian Turner did a lap around the High Commission gardens with the Commonwealth baton for the benefit of photographers and television crews. The baton, made in Glasgow, contains a piece of granite from Ailsa Craig, further endorsing its Scottish credentials.
"The Games are an inspiration for Kenyan youth and those all around the Commonwealth," reiterated Keino in his many speeches to children in the following days of the Kenyan leg of the Baton Relay.
"Unity, love and peace" were the underlying principles on which the Games were built, Keino reminded adults and children alike. His remarks were made all the more poignant by the fact that many of those Kenyan children who stood before him had grown up in Nairobi's slums where division, hatred and violence were the more common experience.
Although Catherine Moraa was not there to hear Keino's clarion call for sport, she is living testimony to what it can offer even the most disenfranchised youngster. On the day we met it was in what has become known as the Sunken Car Park.
Sitting in the centre of dowtown Nairobi, the Sunken Car Park is, for most of the time just that, a car park in a city with notorious traffic congestion. Every Sunday, though, it reverberates to the sound of laughter and squeals of delight as it becomes a vast urban rollerblading arena.
With support from the United Nations Children's Fund (UNICEF) community groups transform the Sunken Car Park into an improvised sports space where youth leaders - many former gang members turned skating instructors - give children the chance to participate in something inconceivable in the slums.
In Catherine Moraa's case it was meeting one of these youth leader skating instructors, who came from the same hard streets and talked her language, that helped open her eyes to life beyond the slum.
"I met people that were like me but saw things differently from what was expected in the ghetto, so I too became a skating trainer," she says.
As we chatted, youngsters too poor to afford the few Kenyan shillings to hire skates let alone buy them, flew past on "blades" often given free by the youth leaders.
Dickson Kahuki is a slum kid but he proudly owns his own skates. So hooked has the 15-year-old become on the sport that it has consumed his life in a way drugs have his friends in the Embakasi slum of Nairobi where he lives.
"All my friends there are into drugs and snatching [robbery], but I like skating so much I even practise my stunts at home before coming here to the car park," he says. I asked Dickson how he managed to get all the way from the estate to downtown Nairobi.
"I put on my skates, and sneak up behind a Mutatu [minibus taxi], grab the roof rack and it pulls me along," he says with a grin.
"I want to be one of them," he continues, pointing to the single file formation of fully equipped skaters that shoots past. All are members of the Kenyan National Team, and most are from the slums. The team has travelled the world representing Kenya in speed skating and distance events, an opportunity most slum kids would have thought impossible in the past says Joel Obanda, another boy from the rougher side of town who is now national coach and runs the Nairobi Eastlanders Roller Skating Club. That day as I said my goodbyes to the "crew" at the car park, I asked if they would be here the following week .
"Of course," replied Catherine Moraa. "It's my 19th birthday this weekend, I've never had a gift in my life, and this is as good as one."
The Herald and Sunday Herald Children of the Commonwealth series will run over the coming months as the Queen's Baton travels the world on its way to Scotland.
As well as bringing our readers inspiring stories from key locations on the baton route, we're also raising money for UNICEF, an official charity partner of the 2014 Commonwealth Games in Glasgow.
There are a number of different ways to donate: you can call 0800 044 5777; or you can click on unicef.org.uk/herald; or you can text 'CHILD' to 70111 to donate £3.
If you prefer, there is a coupon in the Saturday Herald magazine and in the Sunday Herald. UNICEF is the world's leading children's organisation, working to save and change children's lives.