It all began with a phone call - a woman's voice that sounded distressed as she said, 'I've been told you can get rid of evil spirits.'

I had to say that no, I investigated hauntings and other psychic phenomena but exorcism wasn't in my line.

'Well, will you come anyway?' she pleaded. 'Perhaps you can explain what's happening here, tell me I'm not going crazy.'

That was how I came to hear of the house which my caller, Rita Beckett, said had been causing her family trouble for almost a year, and of course I immediately agreed to visit.

Fifteen months earlier Rita and Alan Beckett, together with their sons Christopher, aged eight, Gavin (six) and Keith (four) had moved into the Victorian terrace in Higson Street, Salford, which is an industrial city in the north-west of England. Previously they had lived with Rita's widowed mother in nearby Eccles while seeking an affordable home of their own - anything to get them out of cramped digs, Rita said.

The house in Higson Street had been built for textile mill workers in the 1860s and even after some improvement it remained at best basic: parlour, lounge, scullery, and three tiny bedrooms; no garden or inside lavatory, no central heating. The cobbled neighbourhood included Archie Street, on which the popular English TV programme 'Coronation Street' had been modelled, while a couple of minutes away, across the main road, lay Salford Docks at the end of the Manchester Ship Canal. It was a run-down, dreary area, and seemed all the more so when I arrived on a drizzly November evening.

Rita Beckett, at 32, looked careworn with lines around the eyes and the pinched features that come from hard circumstances and, as she told me, the circumstances had been getting harder.

'It started just before last Christmas,' she said. 'We were in bed one night talking quietly when the door at the bottom of the stairs opened, and it didn't close again. After a few seconds somebody began stomping upstairs, dragging their feet. We thought it must be one of the boys and that surprised us as we hadn't heard them leave their bedroom. You can't creep about in this house because all the boards and stairs squeak like crazy, and the stairs aren't carpeted. Anyway, Alan called out, "What are you doing?" The footsteps stopped straight away. We both got up and turned on the light, and found the staircase empty. Not only that, but the door at the bottom was still closed, as we'd left it. We checked on the boys, who shared a bedroom, and they were all asleep.'

Alan took up the story. 'There'd been odd funny things before that,' he said. 'For instance, we'd find coats on the floor instead of hanging on the wardrobe, but we never really thought much of it. After we'd heard these footsteps we tried to convince ourselves it must have been the neighbours next door but we knew it wasn't. The walls are fairly thin and we can hear them if they have a row or if their kids clatter about, but this sound came from our house, not theirs.'

The first really disturbing experience occurred the following week when Rita and the boys were in the house alone, Alan being at a factory some miles away where he worked night shifts on alternate weeks.

'At about two in the morning Gavin came and woke me up,' Rita recalled. 'He said, "Tell the old man to stop stroking my hair." Of course I thought he'd been dreaming and put him back to bed. But half an hour later he woke me up again and said he couldn't sleep because of the old man who kept touching his hair. I asked what the old man looked like and he said, "He's sort of bent and he smells."

'I went into the boys' bedroom and found nothing unusual except for a dirty, musty smell. I tucked Gavin in again and told him to stop making up stories, then I got back to my own bed and fell asleep.

'I don't know how long I slept but I jolted awake when the bed springs suddenly sank on one side as if somebody had come and sat there. The room wasn't completely dark because of a street light outside the window. I couldn't see anyone but I noticed the same smell as in the boys' room - dirty and musty. Then all at once a hand touched my hair and began stroking it. I think I yelled, and jumped out of bed. When I turned on the light everything looked normal but I could feel somebody moving about, like a cold draught. I just ran out, grabbed the boys and took them downstairs with me.'

Alan returned from work a few hours later to find his family in the lounge, huddled together in blankets. He listened with concern but no real belief to his wife's story.

'I tried to tell her she'd imagined someone touching her,' he said. 'To be honest I closed my mind to anything other than that.'

He had to revise his opinion a few nights later, however.

He told me, 'At some time after two in the morning I heard the door opening at the foot of the stairs, just like before, and then came the footsteps. They were slow and heavy, and I thought I could hear a tapping like a walking stick. This time we had a night light burning on the landing because Rita and the boys had been nervous since the last episode. I went out determined to find out what all this was about. I wasn't scared, just bloody angry. I got to the top of the stairs and immediately saw that the door at the bottom remained shut, and the stairs were empty - yet the footsteps kept coming up. Then something clammy brushed by me, like a cold wind, or cobwebs. A peculiar feeling. The steps went on along the landing towards the third bedroom, which we don't use, and then stopped.'

Rita joined her husband on the landing, and they saw that the door to the third bedroom stood ajar.

'We always keep the door closed,' Rita said. 'I don't know why � I just never like passing that room with the door open. It gives me the creeps for some reason. We went inside and found Gavin sitting on the floor cross-legged, rocking backwards and forwards in the darkness. He looked at us and said in a peculiar voice, kind of croaky, "I'm still here". Then he went on rocking like before.'

'Usually he won't go in that room,' Alan said. 'None of the boys will � they don't like it. And I admit that it does have a bad atmosphere. That's why we don't use the place.'

After this the family became plagued almost nightly by footsteps on the stairs; and Gavin, previously a lively, bright boy became increasingly morose. He expressed a deep fear of the house, and especially of that third bedroom, yet paradoxically he displayed the utmost reluctance to go outdoors. He also began talking about 'the Body', apparently a presence he could see in the house although he found it difficult to describe. Apparently it was not the 'bent old man' he had spoken about previously, as he also continued to see this man at night and seemed to grow fond of him.

'The neighbours told us that the people who lived here before us were called Albert and Dora Owen,' Rita said. 'Dora died of cancer here, and Albert died in hospital about six months later. He was an old man, seventy-eight, and apparently he walked with a stoop. I'm sure it must be him that's haunting us. All the neighbours said the Owens were a lovely couple, very friendly. Yet if so, why do I feel that the presence here is so evil?'

Rita's nerve broke a few days before she contacted me.

'I couldn't sleep so I went downstairs at about three in the morning,' she said. 'Suddenly a cold wind passed right through the room and the transistor radio went off. When I looked up, Gavin was standing in the doorway at the bottom of the stairs, and he laughed in a really malevolent way and said, "I'm still here". That's what he'd said the night we found him alone in the dark. The voice hadn't been his then, and it wasn't now. It sounded harsh. I shouted something at him, and then he seemed to wake up and began crying. I'm convinced the spirit of Albert Owen is in the house and it wants to drive us out.'

I asked about the other boys, if they had seen or sensed anything evil.

'Neither of them will go upstairs on their own, and they're petrified when the footsteps come at night,' Alan said. 'Chris said he felt as if someone kept watching him, but maybe that's down to imagination. God knows there's enough happened here to set anybody's imagination going.'

After our talk I was taken by Rita and Alan through the house. I am not psychic, and not one of those people who claim to be aware of unseen presences. One did not need super sensitivity, however, to feel uncomfortable in the third bedroom of this house. The place exuded malice. The old adage says that walls have ears. These walls seemed to have eyes instead, hostile and glaring. Not a scientific description, maybe, but it describes the room well enough. More mundanely, it had a bare, gritty floor, old wallpaper peeling in places, and a sash window with net curtain. It felt cold as one would expect, but not just ordinarily cold as on any November evening. Here I found a bone-deep chill as though even its essence had been sucked away. I've experienced similar chill in other haunted places and it is always profoundly unpleasant.

'Now you understand why none of us likes this room,' Alan said.

We continued our tour of the house, which apart from that third bedroom felt normal enough, and at the end I told the Becketts I would like to spend some time there and conduct tests.

A week later the family went to stay for a few days with Mrs Beckett's mother, and during that time they allowed me and three colleagues to move in. I spent three nights and two full days in the house with Arthur Latham, Ross Price and Martin Hodgkiss, all of whom had accompanied me on previous investigations. We took regular temperature readings in the rooms, monitored four tape recorders, and set up a movement-sensitive camera in the third bedroom. In addition Arthur, our electronics expert, installed a range of equipment to test atmospheric pressure, shifts in the house structure, and sensors to detect movement on the stairs and in each of the bedrooms.

We of course experienced all the usual noises - creaks, raps, bangings - to be expected in any house of whatever age. We could also hear the television sets in both adjoining houses, and at times it seemed the families had regiments of children running riot. All these things, however, were straightforward and unambiguous.

Not everything else was. On our first night I took up position at the top of the stairs on the landing, Ross in the boys' bedroom and Martin on the threshold of the third bedroom, while Arthur remained in the lounge monitoring our equipment. In each room we had a low-power bulb burning, and all interior doors were open. At 2.13am we clearly heard the distinctive squeaking sound of the door at the bottom of the stairs opening (despite it being already open), and almost immediately footsteps began slowly ascending. Being on the landing, I could see both the staircase, which was in deep shadow but empty, and the open door. The footsteps continued for several seconds but did not reach the top.

This process was repeated twice more that night, at 3.11am and 3.34am. During the night our thermometers registered no undue fluctuation except in the third bedroom, where there were extraordinary swings ranging from 30F to 46F. Perhaps the most interesting, and certainly most sinister, phenomenon occurred in that room. At 2.24am Martin and I both heard movement there. The sound, like someone dragging their feet across the uncarpeted floor, continued for seven minutes although nothing could be seen. I joined Martin at the doorway and immediately noticed the extreme chill billowing out, and a sense of menace that had the hairs on our necks bristling. We were satisfied that the noise came from the room itself and not from the adjoining houses, nor from the walls or loft. We could also discount mice and rats in the eaves and behind the skirtings: the previous afternoon we had gone over the house thoroughly for signs of vermin and there were none; and in any case the sounds Martin and I heard were not the sort made by rodents. Our movement-sensitive camera remained inactive.

With the dawn we compared notes, and Arthur reported that his equipment had indicated sounds being recorded in the third bedroom at the time Martin and I specified. We ran back the tape to that point and listened to the recording. What we were not prepared for was the sound of a human voice: something we had not heard during the night. It emerged deep, hoarse and muffled, and it said just one word, repeated three times. The word may have been 'Gaffing' or 'Gadding'. It could just as easily have been 'Gavin'.

Ross, Martin and I switched positions for the second night, and again for the third. There were more footsteps on the staircase on the second night, at 3.19am, and again the tape recorder picked up a voice in the third bedroom, although this time we couldn't even guess at the word or words. The third night passed peacefully, as did all the daylight hours.

I spoke to several other residents of Higson Street and from them learned that Albert and Dora Owen had lived in the house since at least the 1920s and that there had never been any suggestion of strange occurrences there.

I managed to trace Mr and Mrs Owen's son Derek, who now lived in North Wales, and from him heard a slightly different story. He had grown up in the house and had occupied the third bedroom as a boy, but always felt uncomfortable there and suffered constant nightmares until moving into another room. In addition, his mother had sometimes spoken of feeling uncomfortable in the upstairs rooms - 'She used to say somebody seemed to be hovering over her,' Derek said. He also told me of a rumour that someone had once hanged themselves in the house but I was unable to verify this either through the landlord or through library records.

My opinion, passed to Rita and Alan Beckett, was that there were at least two presences in the house, one benign and the other most definitely not. I thought it possible that the footsteps on the stairs were caused by the ghost of Albert Owen, and that though they might find this phenomenon disconcerting, it would not harm them and was likely in time to disappear. I could not say the same for the presence in the third bedroom, however. Rita and Alan were anxious to have both presences removed if possible and I contacted a priest whom I knew had conducted exorcisms elsewhere.

The priest and two colleagues spent five hours at the house in mid-December, reporting that they all experienced a deep sense of evil in the third bedroom and, to a lesser extent, elsewhere in the house. They were convinced, however, that their exorcism had succeeded and that the presences had been banished.

Rita and Alan did not agree. In fact I found Rita distraught when I next contacted her. She said that twice more she had felt a presence in her bedroom at night, and that Gavin had apparently been possessed three times by the mysterious 'Body'. In early February the family moved out of the house for good, and an elderly couple - similar in age to the Owens - took up occupation in May.

I called on this couple after a few weeks and asked if they had experienced anything unusual. The lady, Elsie Grainger, said, 'If you mean have we heard old Albert on the stairs, the answer's yes. But we don't mind. He's just keeping an eye on the place where he used to live.' I asked specifically about the third bedroom and Mrs Grainger said, 'The place doesn't feel right, does it? We've boarded up the doorway and don't use it, but sometimes we can hear voices there. We take no notice - that seems to be best, don't you think?'