“I do miracles,” Jennifer Lopez croons in the new movie musical “Kiss of the Spider Woman,” and while the song and Ms. Lopez’s singing are melodious, they can’t save what is often an awkward, uneven film. Despite tunes by legendary composers Kander and Ebb, and committed performances from its leads, the feature can’t reconcile the clashing styles and themes of its bifurcated narrative — part prison drama and part song-and-dance B movie.

Diego Luna (“Andor”) is Valentin Arregui, a political prisoner whose new cellmate, Luis Molina, portrayed by the young actor Tonatiuh, recounts the story and glamor of his favorite movie: a fictional Hollywood musical called “Kiss of the Spider Woman.” This film-within-a-film stars Ms. Lopez, who plays two characters in this meta-extravaganza: a blond, successful woman called Aurora and a strange arachnid temptress called the Spider Woman. Both actors also appear as characters in this musical. 

The setting is Argentina during its brutal military dictatorship, and, unlike the original Manuel Puig novel and the 1993 Broadway show on which the new film is based, director Bill Condon moves the timeline to the regime’s waning months in 1983, giving what little plot there is some urgency. As the men endure boredom, poisoning, and torture, Luis’s chronicle of the movie musical provides them with some respite, though Valentin challenges Luis’s political apathy. The heterosexual, intellectual Valentin and the homosexual, romantic Luis eventually grow close as they banter and help each other, and the give-and-take of their relationship constitutes the movie’s most engaging aspect.

Some readers may be familiar with the 1985 movie adaptation of the book, which was dominated by William Hurt’s languid, mask-like, Oscar-winning performance as Luis. That film chose to streamline the narrative by having Luis relate the plot of a single movie instead of the book’s six, one involving collaboration and resistance at Nazi-occupied Paris. It was a smart choice because this mise en abyme dovetailed with the overall plot of betrayal and political awakening. 

The new version also has Luis recount and embellish one movie, though naturally this motion picture is a musical. Unfortunately, the plot of this musical involves gangsters, idealized rural life, and mythical jungle beasts that no amount of self-aware comments from Luis and Valentin can make palatable or coherent, not to mention bear the weight of metaphorical allusion with the two men’s predicaments. 

When he’s not rhapsodizing over his favorite movie, Luis also imagines communing with its lead actress, Ingrid Luna, also played by Ms. Lopez. This leads to arguably the musical’s biggest number, “Where You Are,” a catchy paean to escaping reality through cinema. 

The problem is that it’s staged so rotely — with prison bars, chorus boys, and stair choreography — that one wishes the film had been envisioned with more verve and gaudy imagination. The material itself, with its sometimes distasteful swings between harsh history and sentimentalism, calls for someone like Baz Luhrmann to give it the oomph it needs. The flamboyant director might even have conveyed the work’s occasional critique of consumerist culture more clearly.       

While Mr. Condon is to be commended for presenting the production numbers with a minimum of editing, the writer/director is simply not a visual stylist or a naturally gifted showman, despite having helmed the live-action movie musical version of “Beauty and the Beast” as well as “Dreamgirls.” His fortes lie in dialogue and creating quiet, pensive moments — not in crafting musical numbers. 

A couple of these do sparkle, like the darkroom dance between Ms. Lopez and Mr. Luna during “An Everyday Man.” For the most part, though, the song setpieces feature lighting but no atmosphere, movement but no sensuality, earnestness minus charm, and kitsch without the fun. 

Multiple contemporary issues echo beyond the confines of Valentin and Luis’s cell, such as political violence, resistance, the limits of ideology, equality, and sexuality. These myriad topics don’t come off like checked-off talking points, though, and instead are integral to the two characters’ storylines, with the acting by Messrs. Luna and Tonatiuh achieving genuine inquiry. If only the same kind of profundity was attached to Ms. Lopez’s various roles, as the actress is given nothing to do in the musical portions but be gorgeous, tango a bit here and there, and sing in her generally pleasant yet weak voice.   

Mr. Condon nixes nearly all the songs sung within the realist prison section included in the original stage production, mirroring Bob Fosse’s omission of any numbers not performed in the nightclub for the movie version of “Cabaret.” Tellingly, this strategy contradicts a rejoinder by Luis when Valentin points out how no one sings out in real life as they do in musicals: “Well maybe they should.” 

If the filmmakers had taken Luis’s statement to heart, it not only might have helped connect the movie’s two sides but also reinforced its central themes: the mutability of identity and the universality of entertainment. Alas, what we’re left with is a grim, schizophrenic story where most of the songs feel like vague afterthoughts or muddled musings, leaving viewers unlikely to hum a few bars as they leave the theater.