"Nerve" is a cautionary tale of the near future, or tomorrow, telling of a fictional high-stakes online game where watchers pay to watch as they concoct dares for its players to complete in exchange for direct bank deposits. Reckless, yes, but this concept really isn't all that far-fetched until the film topples over in the third act, trading nuance for heavy-handed moralizing. The picture operates best as a romanticized, rule-breaking teen drama about a 17-year-old girl busting out of her comfort zone. In following her increasingly hairy journey into the dark underbelly of fame-obsessed web culture, the story easily could have spoken to the underlying dangers of its premise without needing to spell them out. Alas, directors Henry Joost and Ariel Schulman (2011's "Paranormal Activity 3" and 2012's "Paranormal Activity 4") and screenwriter Jessica Sharzer (TV's "American Horror Story") don't give viewers the credit they deserve. Growing exceedingly convoluted the further it wades into mundane thriller territory, "Nerve" jumps the proverbial shark and loses its nerve.

Responsible high school senior Venus 'Vee' Delmonico (Emma Roberts) is grappling with telling protective single mom Nancy (Juliette Lewis) she wants to go away to a high-priced California arts school rather than accept a scholarship to a local college on Staten Island. Repeatedly reminded by attention-seeking best friend Sydney (Emily Meade) that she never takes chances or fights for what she wants, Vee chooses on a whim to be a player in a 24-hour interactive online game called Nerve. Her first dare—to kiss a stranger—put her in the path of another player, Ian (Dave Franco), the two of them joining forces as they head into New York City for a night of increasingly precarious challenges. Though Vee intends to bow out early, she is soon swept up in the competition and the money she is racking up, in over her head alongside a mysterious young man about whom she realizes she knows nothing.

Based on Jeanne Ryan's 2012 novel, "Nerve" is stylish, involving and finally too overwrought for its own good. Like a game difficult to put down, one is quickly enraptured by the escalating fun and tension of Vee's dares. Her early scenes with Ian additionally hold an anything-is-possible sense of excitement, their motorcycle ride into Manhattan gushingly scored to BØRNS' whimsical pop anthem "Electric Love." Joost and Schulman milk the narrative's more death-defying situations—two involving heights, another less believable one finding Vee guiding a blindfolded Ian as he drives his bike through the city—even as they also highlight the insane irresponsibility of their two protagonists. When the game's deeper, darker corruption is unveiled and threats begin to arise from a higher power, the film loses its way and then all but entirely self-destructs in a twisty, preachy climactic showdown that makes less sense the more one ponders it.

Emma Roberts (2013's "We're the Millers," TV's "Scream Queens") acts as a likable, compelling guide as Vee, but she has understandable trouble selling the script's clumsier melodramatic confrontations. As Ian, Dave Franco (2016's "Neighbors 2: Sorority Rising") is well-cast, but difficult to warm up to since one is instantly suspicious of his motives. Emily Meade (2016's "Money Monster") has a few honest moments as Sydney, Vee's outgoing but internally insecure friend, while Juliette Lewis (2013's "August: Osage County") is tragically underused as Vee's mom Nancy, playing most of her scenes over cell phones. The mother-daughter relationship between Lewis and Roberts demands nurturing, especially upon learning of a family tragedy they have endured and the real reason why Nancy wants to keep Vee close to home, but it is never properly dealt with—or, for that matter, dealt with at all.

For a film that begins by focusing on the reality of its lead character and the crossroad to her future standing before her, "Nerve" dissolves into plot-centric triteness. The script leaves no room for thematic suggestion or ambiguity as it stops dead in its tracks to provide an unconvincing lecture on the impersonal nature of cell phone screens and the guilt of anyone who would dare watch or play a game where human life is treated like expendable fodder for one's fleeting entertainment value. The hasty wrap-up is particularly discouraging, revealing a casual disinterest in Vee's evolution and what she has learned through her unusual experiences. "Nerve" stands on the cutting edge of a dreamt-up but eerily plausible new social-media fad before taking it to ludicrous, illogical extremes and sweeping all potential consequence under the rug. Based on the undeniable promise of its first hour, the film could have been so much more by doing less.