'It could easily happen, in another context, that I would shoot up as well." That's what Susan Dennehy, pregnant with her second child, learned when she entered the dark world of heroin addiction. The users were mothers, living in a health board B&B in Dublin. They were shooting up in front of young children aged three, six and nine.

Then the mothers were lying around the flat all day semi-conscious, while the children played. Children who had already learned to imitate the use of the tourniquet and the snapping of the fingers against the skin to find a vein.

"I still dream about those children," says Dennehy, herself a mother of two, aged six weeks and 17 months.

"I decided not to contact social welfare because I could not morally justify it as I had gone into that world in trust. I wasn't someone going in as a social worker. I didn't feel I had the right to play a part in their destiny one way or the other," says Dennehy, who debated the ethics with her husband, Stephen Harper, a psychologist with a background in addiction counselling.

Dennehy, an independent radio producer, wanted to experience the world of heroin addicts with one simple, impossibly na∩ve, motive: "I wanted to find out what the buzz was. I set out thinking that I could find out honestly: what was the attraction of heroin? What made it addictive? I had the idea that people don't talk about the buzz of heroin because they're afraid we'd all start using it.

"I didn't find out what the buzz was. I found out how awful it is when you don't have it. Users call it 'dying sick' because if you can't get a fix when you need one, you are dying with sickness."

The result of Dennehy's experiences is Rebel Angel, a radio documentary which will be broadcast tonight on RT╔ Radio 1.If you tune in, you will hear addicts "turning on" in front of their children. You will hear them trying to get the children to be quiet in another part of the room - a very small room.

You will want to cry.

The "angel" is Sue, a 30-year-old heroin addict "living between two worlds", as Dennehy puts it, in the sense that Sue has one foot in the next.

Using heroin makes her sick. Not using it makes her sick. Sue cannot function without her fix. She says when she was high, she loved her daughter, Ciara. She says she took heroin so she and her daughter could have a life together. She took it so she could clean the flat. She took it so she wouldn't be "dying sick". She took it so she could go out and rob or deal to get more money to buy more drugs.

"It's like a parallel universe with a totally different set of morals and values," says Dennehy. "We are so far away from it in some ways, but in other ways we are only a needle away. Only one turn-on away from having that life."

Sue was already a mother when she took heroin for the first time, skin-popping the left-overs from two addicted girlfriends. The three were "robbing" together and Sue realised she'd get a larger share of the profits if she used heroin too.

Sue's daughter, Ciara, who is now aged 12, used to encourage her mother to take her "turn on" so she wouldn't have to go to bed at night. Ciara knew that she could stay up and play once her mother was too strung out to pay attention to her. Ciara was passed from friend to friend - effectively abandoned - until her grandparents took her in. She's not the only one in her school to be living with her "gran" because her mother is an addict. One of her best friends is in the same situation.

Dennehy believes Sue is "warm, generous and open-hearted". This is despite the fact that Sue has stolen from people to support her addiction. And despite the fact that Sue, who is HIV-positive, was "trying for a baby". And despite her neglect of her daughter.

Heroin users are not bad people, Dennehy is convinced: it's the drug that makes them do what they do.

These days, Dennehy says, Sue supports her habit by small-time dealing. This involves hanging around the park and picking up a packet when the heroin dealer drops it on the ground. Within seconds, Sue passes it on to the buyer.

That's between visits to the methadone clinic, where Sue gets a daily drug cocktail of methadone, Valium, anti-depressants and sleeping tablets. She's on "harm reduction", which means that if her urine sample is "dirty" (tests positive for heroin), her methadone dose is cut - leading Sue to use more heroin.

Listening to Rebel Angel, it is immediately obvious in this case that "harm reduction" doesn't work. And that social services - as Dennehy puts it - "have no idea what is going on in the world" if young children are being left to watch their parents shoot up in health board B&Bs.

At first, Dennehy was sick to her stomach being in close proximity to people injecting themselves and each other. But after the third or fourth time, Dennehy had become tolerant and was watching closely. She was tempted to help find veins. Seeing the users in panic as they desperately tried to get the "stick" into the neck, the groin, the foot, was the scariest thing Dennehy had seen.

"In hindsight, I think the experience of making Rebel Angel had more of an affect on me than I realised at the time. Going into it, how could I have been so literal-minded and misinformed? The whole world around it is awful and there is no other way to put it. It's hurtful and cruel to the user, to their families and for children to be living in that world, where their mother is sprawled out of her head most of the time. Then you come home to your own privileged children . . ."

Dennehy hopes that those who listen to the documentary will feel "a little bit of sympathy for Sue as a person". She also hopes people will face what is going on around them.

"I was in town with my sister, and she was shocked to see the women users sitting around the Central Bank. There was one mother, off her head, with a little boy aged about four snuggled in beside her. That's what I was trying to do with the programme, to shock people into noticing what is going on. There are lives being lived like this. You can't just pass these people in the street." If we are going to help these people, help their children, we have to have a sympathetic approach to addiction and find some sort of treatment that works, Dennehy believes. "It's not right that those kids are left in that situation."

After listening to her radio documentary, I was dreaming about those children too.

Rebel Angel will be broadcast tonight on RT╔ Radio 1 at 8.02 p.m.

Addiction Awareness Week, organised by the Rutland Centre in Dublin, runs from October 1st-8th, with the theme "Denying the Reality - Denying the Hope". There will be a series of public lectures in Milltown Park Conference Centre, Sandford Road, Ranelagh. Tel: 01-4946358; e-mail: rutland@iol.ie

Website: www.rutlandcentre.org