Dakota Johnson and Jamie Dornan in “Fifty Shades of Grey.” (Universal Studios via Reuters)

This piece discusses the plot of “Fifty Shades of Grey.”

“Fifty Shades of Grey,” Sam Taylor-Johnson’s adaptation of the first volume of E.L. James’s blockbuster erotic trilogy, arrives in theaters this weekend, just in time for Valentine’s Day. To some observers, this may just seem like added pressure. Flowers and chocolates are no longer enough: now women want kinky, accoutrement-enhanced sex with brutally hot billionaires, who also happen to be troubled enough to let us act out our savior fantasies on them.

But, rising sex-toy injury rates aside, the baroque plot of “Fifty Shades” conceals rather more modest aspirations. The most fantastical thing about James’s novels and Taylor-Johnson’s film (which I’ll discuss more next week) about the virginal literature-lover Anastasia Steele (Dakota Johnson) and Christian Grey (“The Fall” star Jamie Dornan), the wealthy, abused BDSM aficionado who sweeps her off her feet, is the dream of a scenario where a woman can explore her sexuality and the limits of what she is willing to consent to without being penalized for it.

Take the franchise’s portrayal of drinking and consent. In both the novel and the movie, Anastasia’s friend José takes advantage of a moment of mutual drunkenness to profess his feelings for her, and to try to kiss her. While Anastasia says no repeatedly, José doesn’t seem inclined to let her go, until Christian shows up to remind him that no means no. The next day, after Ana recovers from her hangover, Christian tells her just how irritated he is that “You didn’t eat, you got drunk, you put yourself at risk.”

But even though Christian assigns Anastasia responsibility for taking care of herself, he’s clear that the bigger violation is José’s. Our discussions about sex and drinking, particularly in college, have become so convoluted that the way “Fifty Shades” cuts through them is kind of a relief. In “Fifty Shades,” Ana owes it to herself to be careful. But if she’s not, an extra layer of custom and courtesy ought to protect her.

When Ana and Christian start negotiating the terms of their relationship, she gets an additional assist in the form of a negotiated contract for what she will and won’t do sexually. For all the Christian of the novel comes across as a stalker — a characteristic that probably stems from his origins as a fan fiction riff on “Twilight” vampire Edward Cullen — when it comes to the contract, he repeatedly makes clear that he wants Ana to know what she’s getting into. He encourages her to do research on dominant-submissive relationships and specific sexual practices.

In fact, the silly-sounding contract also upsets another convention of our conversations about sex and consent. In order for Ana — who is entirely sexually inexperienced before she meets Christian — to figure out what she does like sexually, she does some things that turn out to be not to her taste, or that deeply upset her. But having consented to these experiences once doesn’t mean she’s required to say yes in the future. And she can be emotionally hurt without being required to think of herself as a trauma survivor.

The first book and movie both lead up to a sequence in which Ana asks Christian to hit her as hard as he’d like. The experience is deeply wounding for both of them: Ana recognizes that her limits are different from his, and Christian recognizes that he can’t ask her to have what he’s previously understood to be his ideal relationship. But it’s a mutual tragedy rather than an assault with an attacker and a victim. It can be the former rather than the latter because, for all Christian is still grappling with the abuse he experienced as a child, he’s learned to communicate clearly and forthrightly, and has required the same from Anastasia all along.

The prose in “Fifty Shades” is embarrassing, which is a shame. Hidden under all the corny expressions and tedious e-mails is a true fantasy world, one where Ana’s interest in her sexuality, her willingness to map her limits and her firm refusal of what she doesn’t want make her a hero rather than a slut or a scold. E.L. James makes much of Anastasia’s virginity. But Ana’s initial purity ends up being much less valuable than the experience she acquires along her journey.