The cage was lying directly on the left-side track.

The tram hit it squarely, there was a crunching sound; the tram moved on. The driver did not stop to inspect the damage.

The cage was crushed, bent to one side, and the mesh was torn. The worm had been pushed through the gap, and lay wriggling in two pieces on the tarmac. The crowd drifted away, as though nothing had happened. Quite soon, somebody stood on one separated half of the worm, squashing it. In all likelihood, this person was not aware of what they had done.

Nobody knows what happened to the other half.

Two days later, and at approximately the same time, another cage was found. It was positioned in the same place - on the short section of Market Street that leads away from Piccadilly Gardens in Manchester. Constructed of the same materials as the first one, only this time of slightly larger size, being six inches square, and the same in height. The mesh was of a wider gauge. It had no door.

Inside the cage, a mouse. A mouse, a common field mouse (Apodemus sylvaticus), grey in colour, with clean fur and a long pink tail that swished, contentedly.

Again, a tram was stopped, and the driver tried to move the cage by hand, without success. He then decided to use his vehicle to move it. One or two of the crowd were horrified at this cruelty, and they protested vehemently with the driver. The driver would have no such discussion.

He did not stop to inspect the damage.

The incident was reported on page seven of the Manchester Evening News.

Five days later, a larger cage was found. This one was three feet square, two feet in height, with rigid steel bars down the sides and along the top. It was cemented to the tramlines. Nobody had seen it being placed there. It had no door.

Inside the cage, a dog. A dog, a mongrel dog (Canis familiaris), perhaps a mix of Collie and German Shepherd. It was a light fawn in colour, with patches of muted brown here and there. It was growling and obviously in some distress, the cage being slightly too small for it. The dog turned in a tight circle, again and again, and butted its head against the bars, trying to get its jaws around them.

A large crowd had gathered, and people were pushing to get a closer look. A woman was kneeling down beside the cage, trying to comfort the poor creature. The dog growled at her, in anger, in fear.

A tram was stalled in front of the cage. A long line of buses and other trams were piled up behind the stranded vehicle. Somebody called the police. A squad car arrived in ten minutes, and a puzzled officer radioed for help. Soon, the police had control of the square, diverting traffic, and trying to keep people back as workmen sawed through the bars.

The dog was released, and taken to the police station. The workmen then removed the cage, clearing the roadway.

The incident was reported on the local television news programme that evening, and was picked up by the national media. The story was connected to the first two episodes, with the worm and the mouse. The BBC featured it on the Nine O'Clock News, as the last item.

By now, most of the people of Manchester had heard of the strange happenings, and speculation was rife, in pubs and living rooms, in restaurants and launderettes. Some felt sure it was a political gesture, by an animal liberation organization. Others claimed it was merely a tasteless joke by a madman. Some even saw it as a brilliant piece of art, a trenchant protest at an unfeeling society.

The police, for their part, had made a forensic examination of the dog. Its fur was covered with grass seeds, bits of matted food, and the usual colony of fleas. The only item of real interest was a splash of silver paint found behind one ear. Chemical analysis of the paint revealed it to be of an unknown composition.

The police also examined footage taken from various security cameras in the Gardens. All five cameras had failed to operate during the early hours of the morning.

The next day, a small crowd gathered at the same location. The people were becoming intrigued; they wanted to see what would happen next. To witness the curiosity. Unfortunately, the road was quite clear, and after half an hour or so the crowd dispersed. The next day a smaller crowd waited there, but again, no cage. Each day the crowd got smaller, until people merely passed the spot, idly glancing to see but then continuing on their way.

Twelve days after the dog incident, when nobody cared any more, the fourth cage appeared. This one was the largest yet: twelve feet square, and ten feet high. The bars were spaced at two-inch intervals. It had no door. It must have been set into position during the deserted, early hours of the morning.

Inside the cage, a horse. A horse, a thoroughbred mare (Equus caballus), with a shiny black coat and a midnight-blue mane. It stood four square in the cage, quite still and at ease. Only the occasional harrumph! from its nostrils and the smoke of its breath disturbed the cold air.

The whole area was cordoned off, as the police decided what to do about the obstruction. A large crowd had gathered, increasing in numbers as the hours passed. A camera crew turned up to capture the event, and to add to the confusion. A team of workmen cut through the bars, releasing the horse into the trained hands of a veterinary surgeon. The poor creature was quickly examined, and then loaded into a horsebox. The workmen set about removing the cage. This operation took three hours to complete, and even then the road was ruined.

No traffic passed through Piccadilly Gardens that day.

The incident was reported on all the news programmes, and in every daily paper. A number of websites were set up on the Internet, dedicated to the cages and their various occupants. A round-the-clock police watch was started, and the camera crew and a large group of spectators camped out all night long, just to catch a glimpse of the next cage being erected. Everyone expected that somebody, some group, would surely come forward and claim responsibility. Nobody did.

So, the people waited. It seemed that all of the country was held in the same state of vibrant expectancy.

It took twenty-one days for the last, severely disappointed person to leave the site.

And fifty-seven lonely days after that disappointment…

Inside the cage, a jaguar. A jaguar (Panthera onca), native of Central America; a great snarling beast, breathing hot thoughts of its homeland. Spotted large, with deep black on orange, turning in its own tight circus, bound by the cage, but barely so.

Nobody dared come close; instead a circle of fear formed around the cage. Time and the city slowed to a halt, as though the beast controlled the clock's pace. It took two days to release the creature safely, and even stunned it provoked fear.

The incident was reported around the world, and discussed in Parliament. Crazed pamphlets were published, offering futile explanations; a desperate man came forward to be punished for the incidents. The police dismissed him after two days' questioning. Synopses for books and films were hastily prepared, many of them finding their price. A range of toy cages was put on the market, five in the series, containing exact models of the worm, the mouse, the dog, the horse and the jaguar. Each cage had a different secret mechanism that would unlock the bars and release the creature. They were the most popular gift that Christmas.

And then, nothing. No new cage appeared. Months passed by. People speculated that the process was complete. Talk drained away to memory, and then to dismissal. A few jokes remained, that was all.