We need to talk about Henry Cavill’s hair. While a lot of things don’t quite work in the meta secret agent action comedy “Argylle,” the erstwhile Superman’s flattop is magnificent.

In the movie's opening scene, which is an enjoyably silly riff on all things “Mission: Impossible,” Cavill’s majestic square cut just stands there looking cool as his Agent Argyle disco-dances with an alluring femme fatale (played by Dua Lipa) and veers wildly off course in a madcap chase through Greece.

Then reality steps in, which is both the strength of “Argylle” (★★ out of four; rated PG-13; in theaters Friday) and also its inevitable undoing. Director Matthew Vaughn is a proven commodity in the spy-movie biz with his “Kingsman” universe, and “Argylle” boasts a notable cast and a sensational premise that traverses a fine line between what’s fiction and what’s not. Yet the movie disappoints by fumbling away most of its wins and piling on double- and triple-crosses and other trappings of a bespoke espionage world.

Argylle's high jinks turn out to be a story being told by reclusive spy novelist Elly Conway (Bryce Dallas Howard), author of the wildly popular “Argylle” series, at a book reading. She basks in the glow of the well-received fourth installment, though she also stresses out about the in-the-works fifth novel, wondering how she’s going to end it. So, too, is a shadowy organization called The Division.

Unbeknownst to Elly, whose quiet lifestyle revolves around her keyboard and pet cat Alfie, her literary plots are coming uncannily close to things happening in real life. On the page, Argylle is seeking a master file exposing villainous agents around the globe, and meanwhile, Division honcho Ritter (Bryan Cranston) would also like to know where this thing might be. He sends his goons after Elly, and good-guy spy Aidan (Sam Rockwell) – a scruffy alternative to the dashing Argylle – saves her, sending them on a mission to keep Elly and Alfie safe plus revealing who exactly the real Argylle is.

'Argylle':Claudia Schiffer's cat Chip is purr-fection at London premiere

Reality and fiction increasingly blend for Elly, often in the blink of an eye, and it echoes through the personalities in the film. Vaughn has built a cast that drives home the duality: spies in dad-mode attire versus agents decked out in their cocktail finest. Cavill, Lipa and John Cena (as Argylle’s wingman Wyatt) are all larger-than-life personalities who make sense as characters in the fantastical spy scenes. Meanwhile, Howard and Rockwell are perfect fits for the “normal” people thrown into crazy shenanigans: She channels one heck of a cat mom, while Rockwell gets to be the charming rogue he does so well. 

“Argylle” weaves an intriguing narrative until the major twist happens in Jason Fuchs’ screenplay when the movie takes a turn for the predictable and muddled. Some characters turn personalities on a dime, and others grow more complex, but the movie ends up trying too hard and loses that early fun luster. (That unnecessary confusion bleeds over into our real world: There is an actual "Argylle" book, written by "Elly Conway," though it's not clear who that might be – and a conspiracy theory that it could be Taylor Swift.)

On the whole, "Argylle" just isn’t as exciting or refreshing as what Vaughn did with his stellar “Kingsman: The Secret Service,” a tweak of the James Bond model that sent up the same tropes and cliches but in a more tongue-in-cheek manner. The filmmaker does carry over his penchant for audacious action sequences, such as a reality-bending train brawl with Aidan and Argylle which is a joy. Your mileage may vary on a very absurd bit where two lovers in a fight scene create a tear-gas heart while a Leona Lewis cover of Snow Patrol’s “Run” plays in the background. 

“Argylle” drips with style, from Samuel L. Jackson putting a spin on his Nick Fury archetype to Ariana DeBose (who plays one of Agent Argylle's crew) singing with ‘80s legend Boy George on the film’s funky credits song. Oh, and let’s not forget about Cavill leaning into his “Rocky IV”-era Dolph Lundgren hairdo. Sadly, the movie’s best bits – and teases of what could come next – are left out in the cold by an unsatisfying spy operation.

10 movies you need to stream right now:From 'Underdoggs' to 'Mission: Impossible 7'