What is the theatrical event at the National Theatre’s small Dorfman space that has excited the new year’s hottest competition for tickets – but also comes with warnings about its explicit content? The intriguingly titled When We Have Sufficiently Tortured Each Other, written by Martin Crimp and directed by Katie Mitchell, stars Cate Blanchett, acting at the National for the first time, opposite Stephen Dillane. The NT, foreseeing the interest that Blanchett would arouse, offered tickets for the six-week run only by ballot. The winners of the draw got the chance to buy a seat.

But perhaps the strangest thing about this new work is its source. Crimp’s play, though set in the present day, has used Samuel Richardson’s 1740 novel Pamela as what he calls a “provocation”. The play’s 12 scenes mirror 12 scenes in the novel.

It is a fair bet that few of those lucky enough to get tickets will have read the original, yet Pamela was a bestseller and literary sensation when it was first published, becoming one of the most influential books in the history of European literature. It was the work that made the novel the unstoppable genre of a new age – and, in the eyes of many, made it morally respectable.

It is a tale of extreme sexual harassment. On the death of her mistress, a 15-year-old maidservant, Pamela, finds herself bequeathed to Mr B, her former employer’s son and a country landowner. She tells her parents how handsomely he has behaved to her, giving her “with his own Hand Four golden Guineas”, and saying: “If I was a good Girl, and faithful and diligent, he would be a Friend to me.”

Like any alert reader of the novel, they immediately detect something sinister. “Oh! That fatal Word, that he would be kind to you, if you would do as you should do,” they reply, “almost kills us with Fears.” And they are right. Kindness soon shades into insinuation, and then, to Pamela’s horror, into undisguised attempts at seduction. Mr B does not expect the answer “No”; when he gets it, he is driven to bullying then bribery then elaborate lies – then force. A familiar story, we might think.

The most remarkable thing about the novel is that it is written entirely in letters, almost all of them penned by Pamela herself. We live out her ordeals, day by day, first as she divines her master’s true intentions, then as she combats his tricks and schemes.

For the most part, we know no more than she does. Richardson called this technique “writing to the moment”. Often, it allows actions to intrude directly into the narrative. “ – But I must break off, here’s some-body coming! – ” Pamela’s writing is not just the medium, it is the stuff of the narrative.

Letters have to be hidden and smuggled; they are interrupted and intercepted. Pamela’s letters are her way of explaining herself and vindicating her own conduct. “I love Writing,” she tells her parents. Even when she has been spirited off to Mr B’s isolated Lincolnshire manor house, and cannot send her letters to her parents, she keeps writing.

This may make the novel sound an unlikely candidate for dramatisation, yet much of what Pamela records is combative dialogue. It is in words that she fights with her would-be seducer. He is always trying to win her or trick her, flatter or humiliate her, through speech. In front of other servants, he makes her out to be the “intriguer”, the manipulative one. She is a “slut” and an “equivocator”. Even when they are alone together, he tries to turn all the blame on her. She is the “gypsy” who has goaded him, the “witch” who has tricked him out of his self‑possession.

The unexpected dynamics of their duel have clearly fascinated Crimp. As he puts it, “the man struggles to ‘perform’ being predator” (he is constantly humiliated and/or defeated in this role). Richardson transformed the rake, a character beloved of Restoration literary culture, from a self-assured libertine into an awkwardly deceitful man. Pamela may be lower class, but she is verbally resourceful and up to his ruses, scoffing when he suggests that if she sleeps with him, he will go on to marry her. “What, Sir, would the World say, were you to marry your Harlot? … I am not to be caught by a Bait so poorly cover’d as this!”

Pamela finds out how power works. She begins to realise that her fellow servants are all either intimidated or suborned. Those who are not corrupt are terrified of losing their “places”. The footman she trusts to convey her letters to her anxious parents (“honest John … he is so willing to carry anything for me”) is in fact instructed by her master to take the letters to him. Pamela discovers that even the post-master is in Mr B’s pay.

As another servant tells her: “You don’t know how you are surrounded.” The other squires are all as bad as Mr B. In the neighbouring household, there have been three pregnancies among the young female servants in the past few months. “All the Gentlemen about” take the gratification that is their due. And, of course, the law is no help: as the most important local squire, Mr B is also the justice of the peace. Pamela is on her own.

Explaining his attraction to the novel, Crimp notes how Richardson creates “a sense of enclosure – of being shut in a world that has its own strange rules”. Drama thrives on such constriction. In the novel, Pamela is always pent up, unable to escape the home in which Mr B confines her. Even on the couple of occasions that she gets out of the house and garden, freedom is impossible: one time, she is terrified back to her confinement by two bulls in a neighbouring field (which turn out to be cows). Another time she reaches the road outside the house, only to realise that she can go no further. She has no money and no means of transport. A young woman can go nowhere on her own.

So, she is apparently powerless – yet she does have a peculiar power over Mr B. The sexual politics of the novel are strange and have attracted suspicion from the beginning. Pamela’s “master” is perplexed and fascinated by her stubborn “virtue”. The novel was subtitled Virtue Rewarded, as if to reassure its first readers of its outcome, and its heroine is indeed triumphant. Richardson’s brilliant trick is to have Mr B steal her letters and slowly be converted by them.

He becomes obsessed with getting hold of her writing. The sexual predator is reading alongside us and is made virtuous by doing so. Eventually, he penitently offers Pamela marriage. She has won. (It is presumed that Crimp will have jettisoned the last third of the novel, in which Richardson wearyingly requires Pamela to testify to the happiness of her married life and to win over his friends and relatives, at first outraged that he has married his servant.)

A young woman – we might say, a girl – eventually chooses to marry the man who, not long before, tried to rape her. In order to earn his happy ending, Richardson must make Pamela detect what is good in the man she insists on calling her “master”. “Just now we heard, that he had like to have drown’d in crossing a Stream, a few Days ago, in pursuing his Game. What is the Matter, with all his ill Usage of me, that I cannot hate him?” She keeps hoping for – but also having to doubt – his reformation. Even while she is fighting him, she preserves some perverse affection for him. It is a disturbing mixture of feelings.

Richardson was a most unlikely literary pioneer. The son of a Derbyshire joiner, he had been apprenticed to a printer and risen to become a partner in the firm and to marry his boss’s daughter. With very little formal education, he became a successful entrepreneur. He established his own printing business and, by now a wealthy man, turned to novel writing only in his 50s.

He was low born, vulgar, self-created – like the novel itself. Some mocked his fiction from the first. When Henry Fielding wrote Shamela, soon after the publication of Pamela, he transformed Richardson’s ever-so-modest protagonist into a scheming minx who used her constant talk of her “vartue” to egg on her master, tricking him into marrying her while enjoying sex with a lusty young curate. His hilarious but cynical satire refused to believe in the inflexible “virtue” that sustains Pamela.

Can we believe in it? Can Crimp? How else will he redeem his sexual predator?

• When We Have Sufficiently Tortured Each Other is at the National Theatre, London SE1, until 2 March. nationaltheatre.org.uk