Some might swear it is meant to be, that everything preceding it was merely preparation for this time, this place, but Margaret Finch isn’t the type to believe in foolish notions like fate. Still, no one could be more surprised than she to discover that, in both appearance and character, she is perfect for this mission. For the first time in her twenty-five years, being female is a benefit; being plain and wholly forgettable, an advantage. Following the rules comes naturally to her. There are those that she has been given: to watch but not participate, to listen but not engage. Then there are the strategies she has devised herself: a rummage in a modestly sized handbag can give her the appearance of being occupied for upwards of six minutes.

As a woman, she is not above suspicion, rather beneath it; as a woman she can go to places the male observers can’t. Places like Blackpool’s Open Air Baths. Specifically, the ladies’ changing rooms. She suspects the stalls might have the effect of the confessional, that advice may be sought and secrets shared. But she has been put off the idea, for several days, by the thought of undressing or of seeing other people in a state of undress. Never having owned a bathing suit, she carries only the toolkit she was instructed to compile when she was recruited: a notebook and two sharpened pencils; a stopwatch; a packet of cigarettes and a lighter; five boiled sweets; and a hip flask filled with brandy. Offering a smoke/sweet/swig can be used to distract a subject if they should start to suspect they are under scrutiny.

She has only ever studied the lido from a distance, standing at a vantage point on the South Pier, which juts out alongside. The curved face of white stone always puts her in mind of the Coliseum. Today she steps inside, walking under one of the Renaissance arches leading to the centre, imagining that she will find herself in a combat ring, bracing herself for some distasteful spectacle. People crowd the edges of the pool, some watching from a viewing platform which runs the length of the roof, others trying to make themselves comfortable on the tiered seating which rises up to block the horizon of sea meeting sky. So many people. So much flesh on display. Young women stand in knitted bathing suits, adjusting necklines lowered by the weight of saturated wool. Young men wear only belted shorts, standing with their stomachs drawn tight. There are exposed chests, pale and hairy; legs arranged at lengthening angles; biceps tensed to maximum effect. She finds it all too much. Like meat set out in a butcher’s window. The men and women give each other appraising looks. But all she sees is sinew and flesh. Spots of acne, yellowed toenails, skin blistered where it has burnt in the sun, dimples at the tops of thighs. To her the meat looks tainted. On the turn.

Reaching the changing room, she enters through the turnstile. She could hire a bathing suit from the kiosk, but since she has no intention of wearing one, decides to save herself threepence, and hire a towel for a penny instead. It will make her look as though she intends to swim and, if she carries it across her front, will be a good place to hide her notebook. Walking along the rows of changing stalls, she pushes the door of one that appears to be empty.

‘Hang on!’

But it is too late: Margaret has already seen through the gap between the door and frame. The woman inside is bending over, pulling up her underwear.

‘Sorry!’ The cubicle door slams in her face. She moves on and, not wanting to risk making the same mistake again, waits until she sees an older woman emerge fully dressed. Congratulating herself for hiring a towel, Margaret hangs it over the top of the stall door to make it obvious it is occupied, and removes her shoes. There’s a narrow bench, but she decides not to sit: the bottoms of her legs will be visible to anyone walking past and will look odd unless she gives the impression she is changing. Unpacking her bag, she tries to hear the woman on the other side of the partition, who seems to be talking to a friend further along.

‘So quick,’ one says in a lowered voice. ‘Over just like that.’

‘And did he …?’

‘I think so … There were … afterwards …’

‘And did he say anything about …?’

‘No. Only that he hoped nature would take its course. And that it wouldn’t be long before … well …’

The friend goes quiet for a moment then asks: ‘Did he not try to …’

‘No. Like I say, there was only that. The act itself. I wasn’t sure whether I was supposed to … or …’

It is clear to Margaret that the two women think they are speaking in a code of modesty, but it requires very little intelligence to decipher it. Copying down their words, she writes the act itself = intercourse in the margin of her notebook. Her hunch that she would be able to collect shared confidences has proved correct, though she had not anticipated that they would speak about such intimate matters. Is it because the screens are there to hide their blushes, or is it the removal of clothes that prompts a baring of the soul?

‘It’s all so confusing,’ she hears the first woman whisper. ‘I don’t know what he wants. And it’s not as if you can come right out and ask, is it?’

‘Or come right out and tell him what you want!’

The woman shushes her friend with a laugh, and Margaret wonders what it is they would say if they could. She has overheard plenty of talk from her colleagues about working-class fantasies and patterns of desire. She was warned when she took the job that ‘women like that’ are much more inclined to speak in coarse terms about private matters. But she has not yet collected evidence about the specifics of what they want. As for herself, she has never thought about such things outside her professional role. To invent intimate scenarios would involve her own participation in the imaginary acts – something she has neither the capacity nor inclination to do.

Margaret transcribes every conversation, word for word, continuing to listen as another group of women arrives. Remembering they might see her legs beneath the partition, she takes off her stockings and undresses as far as her slip, grateful that she has chosen to wear a blue floral tea dress with a long line of fabric buttons to keep her occupied. When the neighbouring cubicles welcome new bathers, she makes a show of putting on the dress and stockings again. Her attempts to eavesdrop are thwarted several times by the loud protestations of children. One who (to her mind) seems disproportionately distressed that it is time to leave the swimming pool; two girls (presumably siblings) fighting about who gets to use a shared towel first; and a little boy who is begging his mother to buy him a sword (a word he pronounces with a heavy rather than silent ‘w’). Margaret notes down every detail, next to the exact time, which runs as a ledger in a thin column on the left side of each page.

This cycle of observing, writing, partial dressing and undressing, continues for several hours. It reminds her of the night she took an inventory of men who fed pennies into the Mutoscope peep shows on the pier. They had put their eyes to the viewing window and turned a handle to see a stack of photographs flipping past. The machines had names like ‘What the Butler Saw’, but from what she had seen herself (her diligence required that she look for the sake of her report), the women undressed no further than she was doing now. In the one called ‘Bedtime Beauties’ three young ladies merely brushed their hair and arranged their nightclothes. Do men really find such mundane actions exciting? It all goes back to the moment Eve covered herself with a fig leaf, she supposes. It is the act of hiding parts of the body that makes them alluring because, considered on a purely aesthetic basis, they really have very little to recommend them. Elsewhere in the world, men and women expose every region of themselves. Private parts are considered public, imbued with no more significance than one’s ears or elbows. Women can walk around bare-breasted and arouse no attention at all. But here in Blackpool men pay a fortune to see topless dancers on the stage.

These differences fascinate her: the unspoken codes that unify and define. Decipher those and you can identify transgression. In England, people rely on concepts of taste and propriety, ethics and morals, right and wrong. But there are too many variables in the formula: class, religion, education, gender. As concepts they are not consistent. If they were, she wouldn’t be here right now, gathering data.

The curious thing is that some people seem to understand these unwritten rules instinctively. But from her own experience, Margaret knows it is all too easy to get it wrong: to cross a line, expose or shame yourself without realising. And by then it’s too late.

Until she was eight, she thought people meant what they said, and said what they meant. But on the day she was introduced to Mother, she learnt that, very often, they say the opposite. Father had told her he had a surprise: he had found her a new mummy he was going to marry so they could all be a family and be happy again....