'The Rhythm Section' review: LIer's muscular direction can't save weakly plotted spy thriller

Where are our female action heroes? They're well represented in the cinematic comic-book universes, but we're still waiting for a female Jason Bourne or Bryan Mills or Jack Reacher. There have been recent attempts — "Hannah," "Red Sparrow," "Peppermint" — but they're generally misfires, not strong enough to launch a franchise. Could "The Rhythm Section," starring Blake Lively as an ordinary woman who transforms herself into an assassin, be the one? 

Lively ("The Town," "The Shallows") plays Stephanie Patrick, a young Brit whose bright future — a top student at Oxford, we're told — spirals into crack addiction and prostitution after her family dies in a plane crash. It's an extreme case of survivor's guilt, but Stephanie snaps out of it when a reporter, Keith Proctor (Raza Jaffrey), contacts her with news: The crash was actually a terrorist bombing. Cribbing from his notes, Stephanie tracks down rogue operative Iain Boyd (a steely Jude Law), who will train her to become an avenging angel. 

One obvious inspiration here is Luc Besson's "La Femme Nikita" (1990), another story about a female junkie-turned-assassin, but director Reed Morano (a Long Island-raised filmmaker known for her Emmy-winning work on Hulu's "The Handmaid's Tale") eschews flashy gunplay and acrobatics. Instead, she plays up Stephanie's inexperience and vulnerability. Lively, a slender actress with delicate features, looks as frail as a goth-rocker here, sporting dyed hair and billowy shirts like a member of The Cure; she wins her battles through sheer determination, not muscle-power. In that same spirit, Morano stages two excellent single-take action sequences — one a close-quarters knife-fight, the other a ragged car-chase through Tangier — that thrum with tension and desperation.

What sinks the film, unfortunately, is the slapdash script by Mark Burnell, adapted from his novel. (The title refers to the human body's drumlike heart and basslike lungs.) "The Rhythm Section" is plagued by unanswered questions (what did that reporter need with the clueless Stephanie, anyway?) and implausible details (no, a first-time swimmer cannot cross a miles-wide lake carrying all her belongings). There are also too many easy inventions, from the vaguely defined CIA guy Marc Serra (Sterling K. Brown) to the useful syringe of synthetic super-poison that Stephanie simply finds lying around one day. Morano is trying to achieve a level of realism, but Burnell's never-believable screenplay thwarts her at every turn. 

A little more care with the story might have turned "The Rhythm Section" into a plausible thriller with an intriguing heroine. Instead, it's another miss in a genre that could still use a hit.