The first time that either Babcock or Wainwright saw the mouse was just after it arrived in the lab, as part of a new delivery on a Monday morning. They had only been working there for a few months and they didn’t know each other very well yet. So it was just chance that they were standing side by side next to the mice cage. Their research examined the mating behaviours of mice and they were planning a big new experiment.

The mouse seemed to notice them because it stopped investigating its new home and it gazed right at them. All the other mice ran around, and messed up the clean straw and squeaked incessantly. This one just sat very still. There was definitely something going on behind those black eyes. It looked from Babcock to Wainwright and back again, and they could not stop watching it. Only when it finally lowered its head, did they glance at each other.

Wainwright thought he’d never seen anything so wonderful as Babcock’s gentle eyes or her shiny hair. Even her lab coat seemed blessed with an aura of knowledge. Babcock, in turn, gazed at Wainwright’s witty nose, his thoughtful mouth and his entrancing ears. And they fell in love.

The mouse scurried away to the back of the cage.

Lab mice, if they’re not dosed with something nasty or engineered to fail sooner, usually live for about a year or so. They tend to be well looked after, they’re kept clean and dry, and they’re fed the right sort of food on a regular basis. No cats can get in to terrorise them, and they are excused all traps.

A month after that Monday morning, Wainwright moved into Babcock’s little flat. In the mornings they would cycle to the lab together and in the evenings they would cook spaghetti. At night they always curled up together, partly because the flat was cold and it was a good way of keeping warm. Occasionally Babcock went to the cinema with her female friends, and when she did, Wainwright had a drink with his ex-flatmates.

Out of all the thousands of genes that made up the DNA in this mouse, just three were different to other mice. But this unique combination of mutant genes created slightly different proteins in its body, which supported a slightly different balance of bacteria on its skin and fur. This meant that the mouse smelt a bit odd to the other mice. As a result, they didn’t like to go near it and it had to sleep alone. But every morning it sat near the front of the cage, and Babcock and Wainwright came to say hello to it before they started work. Because they were good at noticing animal behaviour, they saw that the other mice were keeping away and this worried them; perhaps the mouse would be cold at night. And one day they watched as the other mice formed a sort of barricade around the food, preventing it from eating. It didn’t look like the type of mouse which would try and fight for its fair share. It looked too intelligent for that, it probably understood the ultimate futility of physical combat.

They thought about liberating the mouse and bringing it home with them. Of course this was against all the rules, but they knew it would be happier with them and they could look after it and keep it warm and fed. So, in preparation they bought a cage from the pet-shop, and discussed how to sneak the mouse away from the lab without anyone else noticing.

But this was a bit optimistic, because they were not the only ones who had been affected by the mouse. The lab technician left his wife and started seeing one of the lecturers. The cleaner embarked on a passionate affair with the other lecturer. The students all fell in love with each other, in a seething cloud of hormones even more intense than is normal for students.

Soon, everyone in the lab was in a relationship. And everyone was hanging around the mice cage, hoping for a sight of the mouse. The cleaner would pop in at lunch time for a quick look. The students liked to stroke the mouse’s head. But the lab technician was not too addled by love and satisfying sex to bawl them out one day when he caught them actually cuddling the mouse.

The only animals in the lab who did not love the mouse were the other mice. They shunned it and it became stressed, which caused a larger than usual amount of adrenaline to flood its system, which made it ill. Its nose became dry, its whiskers drooped, its eyes lacked their usual lustre and Babcock and Wainwright realised they had to act soon.

But as they crept through the lab that evening after everyone else had left, they sensed something was terribly wrong. The cage was absolutely still; the other mice were nowhere to be seen. The mouse lay on its side, partly covered by straw. It was beautiful, but it was also dead. Babcock burst into tears and Wainwright comforted her.

The next day the lab held a wake. According to lab protocol, a post-mortem should have been carried out but nobody could bear to cut into the mouse’s body, so it was buried with full scientific honours, and the latest copy of Nature was used for a shroud. No lesser journal would do.

Soon after that, Babcock and Wainwright started to write a paper about the mouse. They described how they had observed it living apart from its cage mates, and how it had died sooner than expected. They discussed a link between the other mice shunning it and its death, and possible physiological explanations. And after some lengthy and heated discussions about the appropriateness of referring to their own feelings in a scientific publication, they wrote a footnote to the paper which stated, ‘The authors felt a particular affinity with this mouse.’ Babcock wanted to write more, but Wainwright disagreed.

When they weren’t working on the paper, they stayed at home feeling sad and in their grief they watched too much television and ate too many take-aways. Wainwright complained that they never went out and that life together in the little flat was getting rather dull. Babcock cried and Wainwright apologised. After she went to bed, he texted his ex-girlfriend.

They were not the only people in the lab who were affected by the death of the mouse. A week afterwards, the cleaner shouted at the lecturer who then dumped her. The lab technician made it up with his wife and dumped the other lecturer, who could be heard weeping in the loos every morning. None of the students were on speaking terms. The lab was silent, the atmosphere was oppressive. Wainwright and Babcock tried to avoid it as much as possible and tended to spend more time in the library, working on their models of mouse behaviour.

As a result of this work they were invited to give a presentation at a large conference. The last slide in this presentation was a photo of the mouse. It wasn’t a great photo, the mouse’s fur was ever so slightly blurred but its face was still charming, its eyes were bright and interested, and its whiskers were fanned out in an inquisitive way. In the lecture theatre, over five hundred behavioural psychologists all looked at this photo and then gazed at each other.

But the mouse’s impact was weaker than it had been in the flesh and the next morning many of the psychologists woke up in the wrong beds, feeling ashamed and confused. There was little discussion at the conference that day. Some people left early and several promising collaborations that could have led to interesting science never got off the ground.

After Babcock and Wainwright returned home from the conference, they went to the pub to have a serious talk about their relationship. Wainwright said he was feeling tied down, and Babcock had to remind him that he’d been the one who wanted to move in together.

And there was another problem; the paper was ready to submit to a scientific journal, but they couldn’t agree on which of the two of them should be the first author.

‘It should be Wainwright and Babcock,’ said Wainwright.

‘Nonsense. It must be Babcock and Wainwright,’ said Babcock.

They had done exactly equal amounts of work on this paper, and everything was beginning to seem rather unfair to them. So the paper had to wait while they argued.

Wainwright started to go out drinking more often and came home smelling of beer and perfume. The lab technician resigned and one of the lecturers went on long-term sick leave. Two students failed their PhD vivas.

Maybe, Babcock thought, things would get better if they found another mouse to love. But it seemed very unlikely. They’d seen and worked with many hundreds of lab mice before encountering this one. And because the other mice had disliked it, it could never have mated and so there were no offspring to carry its genes.

But it couldn’t have been the only lab mouse ever to be so appealing to humans. Babcock scoured the scientific literature on mice to see if anything similar had ever happened previously. She found a few possibilities. One paper had a footnote to say that the mouse under study was ‘delightful’ and had been named Daisy. Another paper acknowledged the research councils, the head of the lab and ‘a lovely white mouse who helped us with our experiments’. Another had a postscript which said that the two authors got married shortly after submitting the paper. She showed this to Wainwright who glared at her.

‘If I ever get married I’m keeping my own name,’ she said.

‘We could be Wainwright and Wainwright,’ he replied, ‘That would solve the problem with the paper.’ It was supposed to be a joke, but Babcock wasn’t in the mood and they had the same argument all over again.

The lab was a sad place now. There was an emptiness to it even though it was full of cages of mice and sacks of their feed and straw, and the shelves were cluttered with manuals and notebooks. Babcock couldn’t stand it any more. She couldn’t bear to look at the other mice, they repelled her.

Very early one morning, she went into the lab without turning on the overhead lights on, to avoid waking the sleeping mice. She tiptoed over to the row of mice cages and flipped open all the doors. Then she tiptoed out. She spent the day at home, and while Wainwright was working at the library, she packed his belongings into boxes and stacked them in neat piles by the door so that he would find it easier to take them away.

When he came home he told her about the escaped mice running everywhere in the lab and causing chaos, before he noticed his belongings. Then he wondered out loud who had set the mice free and ruined all the experiments. Babcock didn’t bother to reply.

After he’d left, she thought that she might have had enough of mice for the time being. Then she went online to look for a cat to adopt. There were several photos of suitable cats and they all looked so appealing. She was finding it quite difficult to choose until she found one which was advertised as being a good mouse-catcher.