Displaced in Mullingar:In a smug society that's easily spooked, the Other World is always nearby and the poor are the unruly ghosts, writes Michael Harding.

There's more to Mullingar than just luxury apartments, or clusters of stand-alone mansions in red brick with wrought-iron gates, which rise behind beech trees out in the suburbs.

There are back streets and laneways and littered alleys and grey walls and derelict houses. Rows of small cottages with white plastic doors, and PVC windows awkwardly cemented into 1950s pebbledash facades.

The Travellers' halting site in Mullingar is squashed into low land, between a graveyard and a main road. I've seen children amusing themselves by flinging bottles of water at each other and drenching their clothes. They exist in a limbo of unease, between the screech of cars and the silence of the dead.

Last Saturday, I was standing at a zebra crossing in a poor neighbourhood, when the lights forced a long-axle silver jeep to stop. Stuck on red, it looked like a spaceship flung down onto the wrong moon. In the back seat a little girl gazed out at me. She had blonde hair and a cream waxy face, lavished with make-up. Her anorak was furry and her face was expressionless.

Her eyes stalked me with the terror of a child lost in the dark, until the lights went green and I realised that for her, I was only a ghost.

I often think that in rural Ireland, ghosts relied too much on Wilkie Collins and Edgar Allan Poe to make their presence felt. In Leitrim, visitors from the Other World invariably appeared after dusk, at the top of the stairs in white lace dresses, or wearing top hats, walking behind carriages drawn by headless horses.

Only once did I hear of a Leitrim ghost manifest in broad daylight. And that was a stag. A friend of mine was standing at the clothesline in the high hills, and saw a giant elk on the far headland. It had majestic antlers but in the time it took to peg a sheet to the line, which blocked my friends' view for a moment, the stag had vanished.

But in small towns, ghosts regularly manifest in broad daylight. In Mullingar, everyone is still haunted. It's just that the ghosts are not quite so exotic. They're more substantial. They may incubate as little flecks of fear in the labyrinth of the mind, but they manifest as ordinary people on the street.

I've never been disturbed by clanking chains, creaking doors, or the chanting of pot-bellied monks waddling around the attic. Fortunately, electricity has killed off those exotic possibilities.

And yet the Other World is disturbingly close. The Other World is a deprived housing estate, or a mean street, where garbage lies uncollected. A cul-de-sac of poverty. A place where people in jeeps don't stop for tea. Yes, it is real, but it's a ghostly realm nonetheless.

Come to think of it, most towns have a "hill", a "half-acre", or a "white city", where the poor have been corralled for generations. And just as film stars and pop idols constitute the ordered pantheon of our secular gods, so the poor have become the unruly ghosts of an affluent society.

There is an old man I keep meeting in unlikely places. He has weak eyes, falling eyelids and shaking hands. Last week I saw him in Tesco, stranded in the electrical section, surrounded by flat screen TVs, smoothie makers and juicers. I pointed him back towards the tinned sardines. He moved slowly, with his purse in one hand and his list of messages in the other.

There was something about his slow trajectory up the aisle, which reminded me of a Shinto master. He scoured the shelves for the precise tuna he wanted.

"I have to go to the post office afterwards," he said to me. "To get me pension."

Later that afternoon, I spotted him at counter number seven, collecting his money. His movements were cautious. The purse still in his left hand, and the Tesco bag on his arm.

"How are ye?" I asked.

He looked at me perplexed.

"I met you this morning," I said.

He didn't remember.

He stared into my face for a minute and said, "I have to go home now." When I had posted my letter, I scanned the street expecting to see him again in the slanting afternoon sun, mooching along or clinging to the wall. But there was no sign of him. Maybe he was a Japanese Shinto master. Or my father's ghost, making a brief appearance.

But like the stag, he had vanished.