Liza!

The play's action covers a period of roughly four months, from August to November, 1887. Liza Kemp is an 18-year-old factory worker and the youngest of 13 children, now living alone with her aging and incompetent mother. Very popular with all the residents—both young and old—of Vere Street, Lambeth, she cannot really make up her mind as far as her love life is concerned. She very much likes Tom, a boy her age, but when he proposes to her she rejects him ("I don't love yer so as ter marry yer"). Nevertheless she is persuaded to join a party of 32 who make a coach trip (in a horse-drawn coach, of course) to a nearby village on the August Bank Holiday (A bank holiday is a public holiday in the United Kingdom or in Ireland. There is no automatic right to time off on these days, although the majority of the population is granted time off work or extra pay for working on these days, depending on their contract. The first official bank holidays were the four days named in the Bank Holidays Act of 1870) Monday. Some of the other members of the party are Tom; Liza's friend Sally and her boyfriend Harry; and Jim Blakeston, a 40-year-old father of nine who has recently moved to Vere Street with his large family, and his wife (while their eldest daughter, Polly, is taking care of her siblings). The outing is a lot of fun, and they all get, more or less, drunk on beer. On their way back, in the dark, Liza realizes that Jim Blakeston is making a pass at her by holding her hand. After their arrival back home, Jim manages to speak to her alone and to steal a kiss from her.
Seemingly without considering either the moral implications or the consequences of her actions, Liza feels attracted to Jim. They never appear together in public because they do not want the other residents of Vere Street or their workmates to start talking about them. One of Jim Blakeston's first steps to win Liza's heart is to go to a melodramatic play with her on Saturday night. Afterwards, he succeeds in seducing her, although we never learn where they do it... obviously in the open.
But in the end they do "slide down into the darkness of the passage".
When autumn arrives and the nights get chillier, Liza's secret meetings with Jim become less comfortable and more trying. Lacking an indoor meeting place, they even spend their evenings together in the third class waiting room of a railway station. Also, to Liza's dismay, it turns out that people do start talking about them, in spite of the precautions they have taken. Only Liza's mother, who is a drunkard and a very simple sort of person, has no idea what is going on.
Liza's friend Sally gets married, has to stop working at the factory because her husband would not let his wife earn her own money, and soon becomes pregnant. Liza feels increasingly isolated, with Sally being married now and even Tom seemingly shunning her, but her love for Jim keeps her going. They do talk about their love affair though: about the possibility of Jim leaving his wife and children ("I dunno if I could get on without the kids"), about Liza not being able to leave her mother because the latter needs her help, about living somewhere else "as if we was married", about bigamy -- but, strangely, not about adultry.