The new film adaptation of Mark Burnell’s 1999 thriller, The Rhythm Section, wastes no time in justifying its title: “Think of your heart as the drums,” narrates star Blake Lively. “Your breathing as the bass.” Later, viewers learn that this mantra was part of the training that transformed Lively’s character into a deadly superspy. It’s a tune that espionage thriller fans have heard before—but, like a skilled remixer, director Reed Morano manages to find exciting new beats.

Both the book and film introduce Stephanie Patrick as a down-and-out, self-destructive sex worker in London, who remains devastated by the deaths of her parents and siblings in a plane crash two years before. A freelance journalist named Proctor tracks her down and tells her that the crash wasn’t an accident at all, but an act of mass murder. She wants revenge on the person responsible, and after Proctor is murdered, she finds herself having to go it alone.

From this point, the book and film diverge. In the novel, a man known as Alexander recruits her for a shady spy organization; he sends her to be trained by a man named Boyd, who molds her into a killing machine. She then goes on a series of missions that bring her closer to her target: the leader of an extremist Islamic terrorist organization. Notably, however, her fate is constantly guided by men—her rapist pimp; Proctor; Alexander; Boyd; and a pallid love interest named Frank. In sporadic first-person sections, Stephanie ruminates endlessly on these relationships. It’s a dynamic that many will find familiar, as it recalls the wildly popular 1990 French film La Femme Nikita, about a down-and-out, lawbreaking young woman who’s recruited into a shady, male-dominated spy agency that turns her into an assassin.

The film, as adapted by author Burnell, goes a different way. It not only alters and simplifies the plot, it also jettisons the pimp, Alexander, and Frank, and shoves Proctor offstage within minutes. Boyd (Jude Law) remains, and an information broker named Serra (Sterling K. Brown) still plays a key role—but Stephanie barely seems to give them a thought. Instead, she’s recast as a woman of single-minded purpose. She doesn’t wait to be recruited—she finds Boyd herself, using Proctor’s files. When she takes on a new identity—that of a deceased assassin named Petra—she doesn’t fret at length about who she is, as she does in the book (“There was a time when I thought the divisions were clear. … [A]s for Stephanie Patrick, I have no idea who she is anymore”). In the film, she knows exactly who she is, and what she wants.

Lively’s riveting performance in A Simple Favor (which was also based on a book) showed she is an actress to be reckoned with, and her intense turn here doesn’t disappoint. Director Morano makes the most of it by keeping the camera as close to her as possible—often only inches away. (She deftly used this same technique in “Offred,” the pilot episode of Hulu’s The Handmaid’s Tale, for which she won an Emmy and a Directors Guild of America Award.) As a result, when Stephanie swims in icy water, you feel the chill; when she dodges bullets, you feel them whistling by your head. A car chase through the streets of Tangier is absolutely nerve-jangling:

The end of the film is particularly satisfying, as Stephanie cuts her ties with Boyd; in the final, lingering shot, you can feel her well-earned sense of freedom. She’s similarly unencumbered at the close of the novel, but in Burnell’s 2001 sequel, Chameleon, she’s back under the sway of Alexander once again. Hopefully, a movie sequel will play a different song.

David Rapp is the senior Indie editor.