No mee-maw, mee-maw siren, but the flashing blue lights spell emergency, cueing everyone to get set, go! Ambulance glides to a halt, doors slide open, and Jack (46), strapped to a stretcher, is whizzed through the hospital doors. His pal leaps down beside him.

Jack (not his real name) certainly looks bad. He shivers and shakes as if possessed. What happened? A sideways glance, and the friend mimes that signal, the one that tells you what your right arm is for. Then he steps closer. "He took that Ecstasy stuff, too."

E is everywhere in Dublin, almost a lifestyle accessory for some young people. "But it's very unusual in a man that age," says Dr Shahid Kundi, of the Accident and Emergency Unit (A&E).

Tallaght Hospital, second night, third overdose.

The place is immense: some 3 1/2 acres of treatment and research facilities. The central mall seems longer than O'Connell Street. "You'd wear a pair of shoes out here in a couple of weeks," says a porter, Tommy Quinn.

Its founding hospitals were loved or feared by generations of Dubliners: some 1,600 staff from the inner-city Meath, Adelaide and National Children's Hospitals have now come together under this name. It's historic.

No one is caked with blood so far but in the A&E waiting area, people are experiencing degrees of pain. A wedding ring suddenly cutting off blood supply to a finger; a student nurse with exams in the morning and an injured foot. Jack is rushed past them.

"We don't operate a first-come, first-served policy," Dr Margaret McKay, paediatric consultant in the children's A&E, explained earlier that day. "Patients are ranked one to five with priority assigned in order of illness."

The place is still winding up. Vending machines stand in bubble wrap, waiting to be connected; a single drinking tap spurts water to your foot's command. No television in A&E, just the drama of someone else's distress.

Some people are getting testy: with the car park costing £1 an hour they may have a point. "I've never been at a hospital run so slowly," a tired woman says into a pay phone. Next minute, her name is called.

The technology is dazzling - X-rays generated almost instantly on to computer screens for rapid diagnosis and inspection from every possible angle; a bank of security cameras surfing 29 locations, looking as contemporary as an installation at the new museum of modern art.

But simple things need fixing: a proposed Dublin Bus service sparing the unwell a long walk from the gate will cost 55 pence a trip.

The taxi for Janice Keegan (7), dropping with tiredness after a day when her class went to a Dublin adventure centre and she broke her arm, takes half an hour to arrive.

Security is tight. Earlier that afternoon, a 19-year-old man arrives with two friends, fresh from a theft conviction, complaining of police brutality. The gardai had tried to take his cigarettes from him, he claims, before asking to borrow my hairbrush. My children are just over head lice so I don't advise it and my bag stays closed.

What was he convicted for? "Stealing hubcaps," he replies.

What did he steal hubcaps for? "A tenner."

His girlfriend rushes up to say that the security men won't let her past the entrance hall. I wonder why. "Because of the tracksuit," she says. Security said they recognised the trio from other venues.

Most of the security men and porters have worked around Dublin hospitals and they know the patterns - the usual suspects, the addicts desperate to steal drugs, their families, histories and offences.

Down-and-outs sometimes hang around hospitals, too, but the guards seem to feel compassion for them. Thieves are odious, they believe, they exploit the way people are distracted and vulnerable, especially in A&E.

By midnight the woman with the swollen finger prepares to leave, her wedding ring sliced off. She first put it on 27 years ago, expecting to wear it to her grave. She peers into the blackened inside of her gold band with a kind of sad curiosity: the ring lasted longer than the marriage - she is separated now.

Mark Doherty is called for X-ray. Mark spent an hour doing the cycle from the triage (French for grading or selecting) nurse, who takes the initial medical details to the doctors inside.

"He put his back out playing football two nights ago, and he didn't tell me until the pain became so bad he was doubled up," says his mother. "And we're going to Spain on Saturday morning."

An hour later, a rasping baby carried by a terrified mother passes the unit where Jack lies, much calmer now, wired to a heart monitor because he is tachycardic. I pause by his cubicle; he wants to talk. The nurses are like little mothers, he tells me, but he's not going to stay here.

Why did you take E? I have to ask. Then Jack weeps. He cries like a little boy. "The wife left me, after 20 years, and we'd just bought a new house. I was fixing it up for her and now she wants to sell it. Oh God, I loved her and I don't know what to do."

Ecstasy it is not.